diff --git a/bin/swagger b/bin/swagger
index 0e02853a3..ecaa50483 100755
--- a/bin/swagger
+++ b/bin/swagger
@@ -127,7 +127,7 @@ set_error_handler(function ($errno, $errstr, $file, $line) use ($errorTypes) {
     if (!(error_reporting() & $errno)) {
         return; // This error code is not included in error_reporting
     }
-    $type = @$errorTypes[$errno] ?: 'ERROR';
+    $type = array_key_exists($errno, $errorTypes) ?: 'ERROR';
     error_log('[' . $type . '] '.$errstr .' in '.$file.' on line '.$line);
     if ($type === 'ERROR') {
         exit($errno);
diff --git a/src/Analysis.php b/src/Analysis.php
index ff8465977..b8ae981c9 100644
--- a/src/Analysis.php
+++ b/src/Analysis.php
@@ -51,6 +51,7 @@ class Analysis
 
     /**
      * @param array $annotations
+     * @param null  $context
      */
     public function __construct($annotations = [], $context = null)
     {
@@ -153,12 +154,12 @@ public function getSubClasses($class)
 
     public function getSuperClasses($class)
     {
-        $classDefinition = @$this->classes[$class];
+        $classDefinition = isset($this->classes[$class]) ? $this->classes[$class] : null;
         if (!$classDefinition || empty($classDefinition['extends'])) { // unknown class, or no inheritance?
             return [];
         }
         $extends = $classDefinition['extends'];
-        $extendsDefinition = @$this->classes[$extends];
+        $extendsDefinition = isset($this->classes[$extends]) ? $this->classes[$extends] : null;
         if (!$extendsDefinition) {
             return [];
         }
diff --git a/src/Context.php b/src/Context.php
index 554f57076..065b16e1f 100644
--- a/src/Context.php
+++ b/src/Context.php
@@ -251,7 +251,7 @@ public static function detect($index = 0)
         if (isset($position['line'])) {
             $context->line = $position['line'];
         }
-        $caller = @$backtrace[$index + 1];
+        $caller = isset($backtrace[$index + 1]) ? $backtrace[$index + 1] : null;
         if (isset($caller['function'])) {
             $context->method = $caller['function'];
             if (isset($caller['type']) && $caller['type'] === '::') {
diff --git a/src/Processors/AugmentProperties.php b/src/Processors/AugmentProperties.php
index d41e8b3d3..61b69ea4d 100644
--- a/src/Processors/AugmentProperties.php
+++ b/src/Processors/AugmentProperties.php
@@ -71,7 +71,8 @@ public function __invoke(Analysis $analysis)
                         }
                         $property->type = $type;
                     } elseif ($property->ref === null && $typeMatches[2] === '') {
-                        $property->ref = @$refs[strtolower($context->fullyQualifiedName($type))];
+                        $tmpKey = strtolower($context->fullyQualifiedName($type));
+                        $property->ref = array_key_exists($tmpKey, $refs) ? $refs[$tmpKey] : null;
                     }
                     if ($typeMatches[2] === '[]') {
                         if ($property->items === null) {
@@ -80,7 +81,8 @@ public function __invoke(Analysis $analysis)
                                 '_context' => new Context(['generated' => true], $context)
                             ]);
                             if ($property->items->type === null) {
-                                $property->items->ref = @$refs[strtolower($context->fullyQualifiedName($type))];
+                                $tmpKey = strtolower($context->fullyQualifiedName($type));
+                                $property->items->ref = array_key_exists($tmpKey, $refs) ? $refs[$tmpKey] : null;
                             }
                         }
                         $property->type = 'array';
diff --git a/src/functions.php b/src/functions.php
index 95b68debe..1e2c7359b 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -30,10 +30,10 @@
      */
     function scan($directory, $options = array())
     {
-        $analyser = @$options['analyser'] ?: new StaticAnalyser();
-        $analysis = @$options['analysis'] ?: new Analysis();
-        $processors = @$options['processors'] ?: Analysis::processors();
-        $exclude = @$options['exclude'] ?: null;
+        $analyser = array_key_exists('analyser', $options) ? new StaticAnalyser() : null;
+        $analysis = array_key_exists('analysis', $options) ? new Analysis() : null;
+        $processors = array_key_exists('processors', $options) ? Analysis::processors() : null;
+        $exclude = array_key_exists('exclude', $options) ? $options['exclude'] : null;
 
         // Crawl directory and parse all files
         $finder = Util::finder($directory, $exclude);
diff --git a/tests/SwaggerTestCase.php b/tests/SwaggerTestCase.php
index c767ea41e..8c5438629 100644
--- a/tests/SwaggerTestCase.php
+++ b/tests/SwaggerTestCase.php
@@ -187,7 +187,7 @@ protected function sorted(stdClass $object, $origin = 'unknown')
                     if (gettype($value[0]) === 'string') {
                         $sortFn = 'strcasecmp';
                     } else {
-                        $sortFn = @$sortMap[$property];
+                        $sortFn = isset($sortMap[$property]) ? $sortMap[$property] : null;
                     }
                     if ($sortFn) {
                         usort($value, $sortFn);