diff --git a/composer.json b/composer.json
index 052ee04f..f3042772 100644
--- a/composer.json
+++ b/composer.json
@@ -49,6 +49,10 @@
         "preferred-install": "dist"
     },
     "extra": {
+        "bamarni-bin": {
+            "bin-links": true,
+            "forward-command": true
+        },
         "branch-alias": {
             "dev-master": "5.4-dev"
         }
diff --git a/src/Parser/EntryParser.php b/src/Parser/EntryParser.php
index 5cfa3eef..bfdb3df9 100644
--- a/src/Parser/EntryParser.php
+++ b/src/Parser/EntryParser.php
@@ -164,6 +164,7 @@ private static function parseValue(string $value)
                 });
             });
         }, Success::create([Value::blank(), self::INITIAL_STATE]))->flatMap(static function (array $result) {
+            /** @psalm-suppress DocblockTypeContradiction */
             if (in_array($result[1], self::REJECT_STATES, true)) {
                 return Error::create('a missing closing quote');
             }
diff --git a/src/Repository/Adapter/ApacheAdapter.php b/src/Repository/Adapter/ApacheAdapter.php
index 868033af..af0aae11 100644
--- a/src/Repository/Adapter/ApacheAdapter.php
+++ b/src/Repository/Adapter/ApacheAdapter.php
@@ -50,7 +50,7 @@ private static function isSupported()
     /**
      * Read an environment variable, if it exists.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return \PhpOption\Option<string>
      */
@@ -65,8 +65,8 @@ public function read(string $name)
     /**
      * Write to an environment variable, if possible.
      *
-     * @param string $name
-     * @param string $value
+     * @param non-empty-string $name
+     * @param string           $value
      *
      * @return bool
      */
@@ -78,7 +78,7 @@ public function write(string $name, string $value)
     /**
      * Delete an environment variable, if possible.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return bool
      */
diff --git a/src/Repository/Adapter/ArrayAdapter.php b/src/Repository/Adapter/ArrayAdapter.php
index 2881a7e1..df64cf6d 100644
--- a/src/Repository/Adapter/ArrayAdapter.php
+++ b/src/Repository/Adapter/ArrayAdapter.php
@@ -40,7 +40,7 @@ public static function create()
     /**
      * Read an environment variable, if it exists.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return \PhpOption\Option<string>
      */
@@ -52,8 +52,8 @@ public function read(string $name)
     /**
      * Write to an environment variable, if possible.
      *
-     * @param string $name
-     * @param string $value
+     * @param non-empty-string $name
+     * @param string           $value
      *
      * @return bool
      */
@@ -67,7 +67,7 @@ public function write(string $name, string $value)
     /**
      * Delete an environment variable, if possible.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return bool
      */
diff --git a/src/Repository/Adapter/EnvConstAdapter.php b/src/Repository/Adapter/EnvConstAdapter.php
index 9ef7fb4d..67752827 100644
--- a/src/Repository/Adapter/EnvConstAdapter.php
+++ b/src/Repository/Adapter/EnvConstAdapter.php
@@ -33,7 +33,7 @@ public static function create()
     /**
      * Read an environment variable, if it exists.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return \PhpOption\Option<string>
      */
@@ -41,6 +41,9 @@ public function read(string $name)
     {
         /** @var \PhpOption\Option<string> */
         return Option::fromArraysValue($_ENV, $name)
+            ->filter(static function ($value) {
+                return \is_scalar($value);
+            })
             ->map(static function ($value) {
                 if ($value === false) {
                     return 'false';
@@ -50,17 +53,15 @@ public function read(string $name)
                     return 'true';
                 }
 
-                return $value;
-            })->filter(static function ($value) {
-                return \is_string($value);
+                return (string) $value;
             });
     }
 
     /**
      * Write to an environment variable, if possible.
      *
-     * @param string $name
-     * @param string $value
+     * @param non-empty-string $name
+     * @param string           $value
      *
      * @return bool
      */
@@ -74,7 +75,7 @@ public function write(string $name, string $value)
     /**
      * Delete an environment variable, if possible.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return bool
      */
diff --git a/src/Repository/Adapter/GuardedWriter.php b/src/Repository/Adapter/GuardedWriter.php
index 7bb69e82..fed8b9ba 100644
--- a/src/Repository/Adapter/GuardedWriter.php
+++ b/src/Repository/Adapter/GuardedWriter.php
@@ -37,8 +37,8 @@ public function __construct(WriterInterface $writer, array $allowList)
     /**
      * Write to an environment variable, if possible.
      *
-     * @param string $name
-     * @param string $value
+     * @param non-empty-string $name
+     * @param string           $value
      *
      * @return bool
      */
@@ -56,7 +56,7 @@ public function write(string $name, string $value)
     /**
      * Delete an environment variable, if possible.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return bool
      */
@@ -74,7 +74,7 @@ public function delete(string $name)
     /**
      * Determine if the given variable is allowed.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return bool
      */
diff --git a/src/Repository/Adapter/ImmutableWriter.php b/src/Repository/Adapter/ImmutableWriter.php
index 574fcd69..399e6f9b 100644
--- a/src/Repository/Adapter/ImmutableWriter.php
+++ b/src/Repository/Adapter/ImmutableWriter.php
@@ -45,8 +45,8 @@ public function __construct(WriterInterface $writer, ReaderInterface $reader)
     /**
      * Write to an environment variable, if possible.
      *
-     * @param string $name
-     * @param string $value
+     * @param non-empty-string $name
+     * @param string           $value
      *
      * @return bool
      */
@@ -72,7 +72,7 @@ public function write(string $name, string $value)
     /**
      * Delete an environment variable, if possible.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return bool
      */
@@ -99,7 +99,7 @@ public function delete(string $name)
      *
      * That is, is it an "existing" variable.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return bool
      */
diff --git a/src/Repository/Adapter/MultiReader.php b/src/Repository/Adapter/MultiReader.php
index 12b3bda4..0cfda6f6 100644
--- a/src/Repository/Adapter/MultiReader.php
+++ b/src/Repository/Adapter/MultiReader.php
@@ -30,7 +30,7 @@ public function __construct(array $readers)
     /**
      * Read an environment variable, if it exists.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return \PhpOption\Option<string>
      */
diff --git a/src/Repository/Adapter/MultiWriter.php b/src/Repository/Adapter/MultiWriter.php
index e1dcf56b..15a9d8fd 100644
--- a/src/Repository/Adapter/MultiWriter.php
+++ b/src/Repository/Adapter/MultiWriter.php
@@ -28,8 +28,8 @@ public function __construct(array $writers)
     /**
      * Write to an environment variable, if possible.
      *
-     * @param string $name
-     * @param string $value
+     * @param non-empty-string $name
+     * @param string           $value
      *
      * @return bool
      */
@@ -47,7 +47,7 @@ public function write(string $name, string $value)
     /**
      * Delete an environment variable, if possible.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return bool
      */
diff --git a/src/Repository/Adapter/PutenvAdapter.php b/src/Repository/Adapter/PutenvAdapter.php
index 126c4656..6d017cdb 100644
--- a/src/Repository/Adapter/PutenvAdapter.php
+++ b/src/Repository/Adapter/PutenvAdapter.php
@@ -48,7 +48,7 @@ private static function isSupported()
     /**
      * Read an environment variable, if it exists.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return \PhpOption\Option<string>
      */
@@ -63,8 +63,8 @@ public function read(string $name)
     /**
      * Write to an environment variable, if possible.
      *
-     * @param string $name
-     * @param string $value
+     * @param non-empty-string $name
+     * @param string           $value
      *
      * @return bool
      */
@@ -78,7 +78,7 @@ public function write(string $name, string $value)
     /**
      * Delete an environment variable, if possible.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return bool
      */
diff --git a/src/Repository/Adapter/ReaderInterface.php b/src/Repository/Adapter/ReaderInterface.php
index 5ece5ee7..306a63fc 100644
--- a/src/Repository/Adapter/ReaderInterface.php
+++ b/src/Repository/Adapter/ReaderInterface.php
@@ -9,7 +9,7 @@ interface ReaderInterface
     /**
      * Read an environment variable, if it exists.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return \PhpOption\Option<string>
      */
diff --git a/src/Repository/Adapter/ReplacingWriter.php b/src/Repository/Adapter/ReplacingWriter.php
index 326cd187..98c0f041 100644
--- a/src/Repository/Adapter/ReplacingWriter.php
+++ b/src/Repository/Adapter/ReplacingWriter.php
@@ -45,8 +45,8 @@ public function __construct(WriterInterface $writer, ReaderInterface $reader)
     /**
      * Write to an environment variable, if possible.
      *
-     * @param string $name
-     * @param string $value
+     * @param non-empty-string $name
+     * @param string           $value
      *
      * @return bool
      */
@@ -63,7 +63,7 @@ public function write(string $name, string $value)
     /**
      * Delete an environment variable, if possible.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return bool
      */
@@ -83,7 +83,7 @@ public function delete(string $name)
      * Returns true if it currently exists, or existed at any point in the past
      * that we are aware of.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return bool
      */
diff --git a/src/Repository/Adapter/ServerConstAdapter.php b/src/Repository/Adapter/ServerConstAdapter.php
index 8e3dc98e..8fc1d4b0 100644
--- a/src/Repository/Adapter/ServerConstAdapter.php
+++ b/src/Repository/Adapter/ServerConstAdapter.php
@@ -33,7 +33,7 @@ public static function create()
     /**
      * Read an environment variable, if it exists.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return \PhpOption\Option<string>
      */
@@ -41,6 +41,9 @@ public function read(string $name)
     {
         /** @var \PhpOption\Option<string> */
         return Option::fromArraysValue($_SERVER, $name)
+            ->filter(static function ($value) {
+                return \is_scalar($value);
+            })
             ->map(static function ($value) {
                 if ($value === false) {
                     return 'false';
@@ -50,17 +53,15 @@ public function read(string $name)
                     return 'true';
                 }
 
-                return $value;
-            })->filter(static function ($value) {
-                return \is_string($value);
+                return (string) $value;
             });
     }
 
     /**
      * Write to an environment variable, if possible.
      *
-     * @param string $name
-     * @param string $value
+     * @param non-empty-string $name
+     * @param string           $value
      *
      * @return bool
      */
@@ -74,7 +75,7 @@ public function write(string $name, string $value)
     /**
      * Delete an environment variable, if possible.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return bool
      */
diff --git a/src/Repository/Adapter/WriterInterface.php b/src/Repository/Adapter/WriterInterface.php
index 8b3fa577..4cb3d61f 100644
--- a/src/Repository/Adapter/WriterInterface.php
+++ b/src/Repository/Adapter/WriterInterface.php
@@ -9,8 +9,8 @@ interface WriterInterface
     /**
      * Write to an environment variable, if possible.
      *
-     * @param string $name
-     * @param string $value
+     * @param non-empty-string $name
+     * @param string           $value
      *
      * @return bool
      */
@@ -19,7 +19,7 @@ public function write(string $name, string $value);
     /**
      * Delete an environment variable, if possible.
      *
-     * @param string $name
+     * @param non-empty-string $name
      *
      * @return bool
      */
diff --git a/src/Repository/AdapterRepository.php b/src/Repository/AdapterRepository.php
index ada1c458..e4b8fb78 100644
--- a/src/Repository/AdapterRepository.php
+++ b/src/Repository/AdapterRepository.php
@@ -6,6 +6,7 @@
 
 use Dotenv\Repository\Adapter\ReaderInterface;
 use Dotenv\Repository\Adapter\WriterInterface;
+use InvalidArgumentException;
 
 final class AdapterRepository implements RepositoryInterface
 {
@@ -46,7 +47,7 @@ public function __construct(ReaderInterface $reader, WriterInterface $writer)
      */
     public function has(string $name)
     {
-        return $this->reader->read($name)->isDefined();
+        return '' !== $name && $this->reader->read($name)->isDefined();
     }
 
     /**
@@ -54,10 +55,16 @@ public function has(string $name)
      *
      * @param string $name
      *
+     * @throws \InvalidArgumentException
+     *
      * @return string|null
      */
     public function get(string $name)
     {
+        if ('' === $name) {
+            throw new InvalidArgumentException('Expected name to be a non-empty string.');
+        }
+
         return $this->reader->read($name)->getOrElse(null);
     }
 
@@ -67,10 +74,16 @@ public function get(string $name)
      * @param string $name
      * @param string $value
      *
+     * @throws \InvalidArgumentException
+     *
      * @return bool
      */
     public function set(string $name, string $value)
     {
+        if ('' === $name) {
+            throw new InvalidArgumentException('Expected name to be a non-empty string.');
+        }
+
         return $this->writer->write($name, $value);
     }
 
@@ -79,10 +92,16 @@ public function set(string $name, string $value)
      *
      * @param string $name
      *
+     * @throws \InvalidArgumentException
+     *
      * @return bool
      */
     public function clear(string $name)
     {
+        if ('' === $name) {
+            throw new InvalidArgumentException('Expected name to be a non-empty string.');
+        }
+
         return $this->writer->delete($name);
     }
 }
diff --git a/src/Repository/RepositoryInterface.php b/src/Repository/RepositoryInterface.php
index a2a7d32f..d9b18a40 100644
--- a/src/Repository/RepositoryInterface.php
+++ b/src/Repository/RepositoryInterface.php
@@ -20,6 +20,8 @@ public function has(string $name);
      *
      * @param string $name
      *
+     * @throws \InvalidArgumentException
+     *
      * @return string|null
      */
     public function get(string $name);
@@ -30,6 +32,8 @@ public function get(string $name);
      * @param string $name
      * @param string $value
      *
+     * @throws \InvalidArgumentException
+     *
      * @return bool
      */
     public function set(string $name, string $value);
@@ -39,6 +43,8 @@ public function set(string $name, string $value);
      *
      * @param string $name
      *
+     * @throws \InvalidArgumentException
+     *
      * @return bool
      */
     public function clear(string $name);
diff --git a/tests/Dotenv/Repository/Adapter/EnvConstAdapterTest.php b/tests/Dotenv/Repository/Adapter/EnvConstAdapterTest.php
index 592f304e..8e10b711 100644
--- a/tests/Dotenv/Repository/Adapter/EnvConstAdapterTest.php
+++ b/tests/Dotenv/Repository/Adapter/EnvConstAdapterTest.php
@@ -35,7 +35,7 @@ public function testTrueRead()
 
     public function testBadTypeRead()
     {
-        $_ENV['CONST_TEST'] = 123;
+        $_ENV['CONST_TEST'] = [123];
         $value = self::createAdapter()->read('CONST_TEST');
         self::assertFalse($value->isDefined());
     }
diff --git a/tests/Dotenv/Repository/Adapter/ServerConstAdapterTest.php b/tests/Dotenv/Repository/Adapter/ServerConstAdapterTest.php
index 7366b79a..d322f779 100644
--- a/tests/Dotenv/Repository/Adapter/ServerConstAdapterTest.php
+++ b/tests/Dotenv/Repository/Adapter/ServerConstAdapterTest.php
@@ -35,7 +35,7 @@ public function testTrueRead()
 
     public function testBadTypeRead()
     {
-        $_SERVER['CONST_TEST'] = 123;
+        $_SERVER['CONST_TEST'] = [123];
         $value = self::createAdapter()->read('CONST_TEST');
         self::assertFalse($value->isDefined());
     }
diff --git a/tests/Dotenv/Repository/RepositoryTest.php b/tests/Dotenv/Repository/RepositoryTest.php
index 8f36f885..ce296dc6 100644
--- a/tests/Dotenv/Repository/RepositoryTest.php
+++ b/tests/Dotenv/Repository/RepositoryTest.php
@@ -165,7 +165,7 @@ public function testGettingVariableByName()
         self::assertSame('bar', $repo->get('FOO'));
     }
 
-    public function testGettingBadVariable()
+    public function testGettingNullVariable()
     {
         $repo = RepositoryBuilder::createWithDefaultAdapters()->make();
 
@@ -174,6 +174,16 @@ public function testGettingBadVariable()
         $repo->get(null);
     }
 
+    public function testGettingEmptyVariable()
+    {
+        $repo = RepositoryBuilder::createWithDefaultAdapters()->make();
+
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Expected name to be a non-empty string.');
+
+        $repo->get('');
+    }
+
     public function testSettingVariable()
     {
         $this->load();
@@ -185,7 +195,7 @@ public function testSettingVariable()
         self::assertSame('new', $repo->get('FOO'));
     }
 
-    public function testSettingBadVariable()
+    public function testSettingNullVariable()
     {
         $repo = RepositoryBuilder::createWithDefaultAdapters()->make();
 
@@ -194,6 +204,16 @@ public function testSettingBadVariable()
         $repo->set(null, 'foo');
     }
 
+    public function testSettingEmptyVariable()
+    {
+        $repo = RepositoryBuilder::createWithDefaultAdapters()->make();
+
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Expected name to be a non-empty string.');
+
+        $repo->set('', 'foo');
+    }
+
     public function testClearingVariable()
     {
         $this->load();
@@ -217,7 +237,7 @@ public function testClearingVariableWithArrayAdapter()
         self::assertFalse($repo->has('FOO'));
     }
 
-    public function testClearingBadVariable()
+    public function testClearingNullVariable()
     {
         $repo = RepositoryBuilder::createWithDefaultAdapters()->make();
 
@@ -226,6 +246,16 @@ public function testClearingBadVariable()
         $repo->clear(null);
     }
 
+    public function testClearingEmptyVariable()
+    {
+        $repo = RepositoryBuilder::createWithDefaultAdapters()->make();
+
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Expected name to be a non-empty string.');
+
+        $repo->clear('');
+    }
+
     public function testCannotSetVariableOnImmutableInstance()
     {
         $this->load();
diff --git a/vendor-bin/phpstan/composer.json b/vendor-bin/phpstan/composer.json
index 684fac88..ac2a0ebc 100644
--- a/vendor-bin/phpstan/composer.json
+++ b/vendor-bin/phpstan/composer.json
@@ -9,6 +9,9 @@
         "thecodingmachine/phpstan-strict-rules": "1.0.0"
     },
     "config": {
-        "preferred-install": "dist"
+        "preferred-install": "dist",
+        "allow-plugins": {
+            "phpstan/extension-installer": true
+        }
     }
 }
diff --git a/vendor-bin/psalm/composer.json b/vendor-bin/psalm/composer.json
index 55355425..fa599500 100644
--- a/vendor-bin/psalm/composer.json
+++ b/vendor-bin/psalm/composer.json
@@ -1,7 +1,7 @@
 {
     "require": {
         "php": "^7.4",
-        "psalm/phar": "4.15.0"
+        "psalm/phar": "4.19.0"
     },
     "config": {
         "preferred-install": "dist"