diff --git a/proposal/myrmidon/src/java/org/apache/myrmidon/components/converter/DefaultMasterConverter.java b/proposal/myrmidon/src/java/org/apache/myrmidon/components/converter/DefaultMasterConverter.java
index 4fbaaf49a..0039e0f76 100644
--- a/proposal/myrmidon/src/java/org/apache/myrmidon/components/converter/DefaultMasterConverter.java
+++ b/proposal/myrmidon/src/java/org/apache/myrmidon/components/converter/DefaultMasterConverter.java
@@ -106,7 +106,20 @@ public class DefaultMasterConverter
                 getLogger().debug( message );
             }
 
-            return converter.convert( destination, original, context );
+            final Object object = converter.convert( destination, original, context );
+            if( destination.isInstance( object ) )
+            {
+                return object;
+            }
+            else
+            {
+                final String message =
+                    REZ.getString( "bad-return-type.error",
+                                   name,
+                                   object,
+                                   destination.getName() );
+                throw new ConverterException( message );
+            }
         }
         catch( final TypeException te )
         {
diff --git a/proposal/myrmidon/src/java/org/apache/myrmidon/components/converter/Resources.properties b/proposal/myrmidon/src/java/org/apache/myrmidon/components/converter/Resources.properties
index f2cc4eeaf..7848babff 100644
--- a/proposal/myrmidon/src/java/org/apache/myrmidon/components/converter/Resources.properties
+++ b/proposal/myrmidon/src/java/org/apache/myrmidon/components/converter/Resources.properties
@@ -4,3 +4,4 @@ found-converter.notice=Found Converter: {0}.
 no-converter-factory.error=Unable to retrieve Converter factory from TypeManager.
 no-converter.error=Unable to find converter for {0} to {1} conversion.
 bad-typemanager.error=Badly configured TypeManager missing converter definition.
+bad-return-type.error=The TypeManager for {0} returned "{1}" which is not of the expected type {2}.