diff --git a/implementation/src/main/java/io/smallrye/config/Converters.java b/implementation/src/main/java/io/smallrye/config/Converters.java
index ba8031f18..0c1b8cbe1 100644
--- a/implementation/src/main/java/io/smallrye/config/Converters.java
+++ b/implementation/src/main/java/io/smallrye/config/Converters.java
@@ -735,7 +735,7 @@ public A convert(final String str) {
             for (String itemString : itemStrings) {
                 if (!itemString.isEmpty()) {
                     final T item = getDelegate().convert(itemString);
-                    if (item != null && !item.equals(",")) {
+                    if (item != null) {
                         Array.set(array, size++, item);
                     }
                 }
diff --git a/implementation/src/main/java/io/smallrye/config/EnvConfigSource.java b/implementation/src/main/java/io/smallrye/config/EnvConfigSource.java
index 8539a5478..75b5d2ad4 100644
--- a/implementation/src/main/java/io/smallrye/config/EnvConfigSource.java
+++ b/implementation/src/main/java/io/smallrye/config/EnvConfigSource.java
@@ -20,6 +20,7 @@
 import static java.security.AccessController.doPrivileged;
 import static java.util.Collections.unmodifiableMap;
 
+import java.io.Serializable;
 import java.security.PrivilegedAction;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
@@ -31,9 +32,11 @@
  */
 public class EnvConfigSource extends AbstractConfigSource {
     private static final long serialVersionUID = -4525015934376795496L;
+
     private static final int DEFAULT_ORDINAL = 300;
+    private static final Object NULL_VALUE = new Object();
 
-    private final Map<String, String> cache = new ConcurrentHashMap<>(); //the regex match is expensive
+    private final Map<String, Object> cache = new ConcurrentHashMap<>();
 
     protected EnvConfigSource() {
         super("EnvConfigSource", getEnvOrdinal());
@@ -50,9 +53,12 @@ public String getValue(String name) {
             return null;
         }
 
-        String cachedValue = cache.get(name);
+        Object cachedValue = cache.get(name);
         if (cachedValue != null) {
-            return cachedValue;
+            if (cachedValue == NULL_VALUE) {
+                return null;
+            }
+            return (String) cachedValue;
         }
 
         final Map<String, String> properties = getProperties();
@@ -80,6 +86,7 @@ public String getValue(String name) {
             return value;
         }
 
+        cache.put(name, NULL_VALUE);
         return null;
     }
 
@@ -133,4 +140,16 @@ private static int getEnvOrdinal() {
 
         return DEFAULT_ORDINAL;
     }
+
+    Object writeReplace() {
+        return new Ser();
+    }
+
+    static final class Ser implements Serializable {
+        private static final long serialVersionUID = 6812312718645271331L;
+
+        Object readResolve() {
+            return new EnvConfigSource();
+        }
+    }
 }
diff --git a/implementation/src/test/java/io/smallrye/config/EmptyValuesTest.java b/implementation/src/test/java/io/smallrye/config/EmptyValuesTest.java
index dfec3701c..79890bcfd 100644
--- a/implementation/src/test/java/io/smallrye/config/EmptyValuesTest.java
+++ b/implementation/src/test/java/io/smallrye/config/EmptyValuesTest.java
@@ -2,118 +2,125 @@
 
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import java.util.ArrayList;
 import java.util.NoSuchElementException;
 import java.util.Optional;
 
 import org.junit.jupiter.api.Test;
 
-// https://github.com/eclipse/microprofile-config/issues/446
+// https://github.com/eclipse/microprofile-config/blob/master/spec/src/main/asciidoc/configexamples.asciidoc#config-value-conversion-rules
 class EmptyValuesTest {
-    @Test // Rule 1
+    @Test
     void missingForArray() {
         assertThrows(NoSuchElementException.class, () -> config().getValue("my.prop", String[].class));
     }
 
-    @Test // Rule 2
+    @Test
     void emptyForArray() {
         assertThrows(NoSuchElementException.class, () -> config("my.prop", "").getValue("my.prop", String[].class));
     }
 
-    @Test // Rule 3
+    @Test
     void commaForArray() {
         assertThrows(NoSuchElementException.class, () -> config("my.prop", ",").getValue("my.prop", String[].class));
-        assertThrows(NoSuchElementException.class, () -> config("my.prop", "\\,").getValue("my.prop", String[].class));
+        assertArrayEquals(new String[] { "," }, config("my.prop", "\\,").getValue("my.prop", String[].class));
     }
 
-    @Test // Rule 4
+    @Test
     void multipleCommasForArray() {
         assertThrows(NoSuchElementException.class, () -> config("my.prop", ",,").getValue("my.prop", String[].class));
     }
 
-    @Test // Rule 5
+    @Test
     void valuesForArray() {
         assertArrayEquals(new String[] { "foo", "bar" }, config("my.prop", "foo,bar").getValue("my.prop", String[].class));
     }
 
-    @Test // Rule 6
+    @Test
     void valuesCommaEndForArray() {
         assertArrayEquals(new String[] { "foo" }, config("my.prop", "foo,").getValue("my.prop", String[].class));
     }
 
-    @Test // Rule 7
+    @Test
     void valuesCommaStartForArray() {
         assertArrayEquals(new String[] { "bar" }, config("my.prop", ",bar").getValue("my.prop", String[].class));
     }
 
-    @Test // Rule 8
+    @Test
     void whitespaceForArray() {
         assertArrayEquals(new String[] { " " }, config("my.prop", " ").getValue("my.prop", String[].class));
     }
 
-    @Test // Rule 9
+    @Test
     void value() {
         assertEquals("foo", config("my.prop", "foo").getValue("my.prop", String.class));
     }
 
-    @Test // Rule 10
+    @Test
     void empty() {
         assertThrows(NoSuchElementException.class, () -> config("my.prop", "").getValue("my.prop", String.class));
     }
 
-    @Test // Rule 11
+    @Test
     void comma() {
         assertEquals(",", config("my.prop", ",").getValue("my.prop", String.class));
     }
 
-    @Test // Rule 12
+    @Test
     void missing() {
         assertThrows(NoSuchElementException.class, () -> config().getValue("my.prop", String.class));
     }
 
-    @Test // Rule 13
+    @Test
     void valueForOptional() {
         assertEquals(Optional.of("foo"), config("my.prop", "foo").getOptionalValue("my.prop", String.class));
     }
 
-    @Test // Rule 14
+    @Test
     void emptyForOptional() {
         assertEquals(Optional.empty(), config("my.prop", "").getOptionalValue("my.prop", String.class));
         assertNotEquals(Optional.of(""), config("my.prop", "").getOptionalValue("my.prop", String.class));
     }
 
-    @Test // Rule 15
+    @Test
     void missingForOptional() {
         assertEquals(Optional.empty(), config().getOptionalValue("my.prop", String.class));
     }
 
-    @Test // Rule 16
+    @Test
     void emptyForOptionalArray() {
         assertEquals(Optional.empty(), config("my.prop", "").getOptionalValue("my.prop", String[].class));
         assertNotEquals(Optional.of(new String[] {}), config("my.prop", "").getOptionalValue("my.prop", String[].class));
     }
 
-    @Test // Rule 17
+    @Test
     void commaForOptionalArray() {
         assertEquals(Optional.empty(), config("my.prop", ",").getOptionalValue("my.prop", String[].class));
-        assertNotEquals(Optional.of(new String[] { "", "" }),
-                config("my.prop", ",").getOptionalValue("my.prop", String[].class));
+        assertTrue(config("my.prop", "\\,").getOptionalValue("my.prop", String[].class).isPresent());
+        assertArrayEquals(new String[] { "," }, config("my.prop", "\\,").getOptionalValue("my.prop", String[].class).get());
+        assertFalse(config("my.prop", ",").getOptionalValue("my.prop", String[].class).isPresent());
     }
 
-    @Test // Rule 18
+    @Test
     void mutipleCommasForOptionalArray() {
         assertEquals(Optional.empty(), config("my.prop", ",,").getOptionalValue("my.prop", String[].class));
-        assertNotEquals(Optional.of(new String[] { "", "", "" }),
-                config("my.prop", ",").getOptionalValue("my.prop", String[].class));
     }
 
-    @Test // Rule 19
+    @Test
     void missingForOptionalArray() {
         assertEquals(Optional.empty(), config().getOptionalValue("my.prop", String[].class));
     }
 
+    @Test
+    void commaForOptionalList() {
+        assertTrue(config("my.prop", "\\,").getOptionalValues("my.prop", String.class, ArrayList::new).isPresent());
+    }
+
     private static SmallRyeConfig config(String... keyValues) {
         return new SmallRyeConfigBuilder()
                 .addDefaultInterceptors()