diff --git a/processor/src/main/java/org/mapstruct/ap/internal/processor/MethodRetrievalProcessor.java b/processor/src/main/java/org/mapstruct/ap/internal/processor/MethodRetrievalProcessor.java
index da9291e91..ed8905bce 100644
--- a/processor/src/main/java/org/mapstruct/ap/internal/processor/MethodRetrievalProcessor.java
+++ b/processor/src/main/java/org/mapstruct/ap/internal/processor/MethodRetrievalProcessor.java
@@ -377,6 +377,18 @@ public class MethodRetrievalProcessor implements ModelElementProcessor<Void, Lis
             return false;
         }
 
+      for ( Parameter sourceParameter : sourceParameters ) {
+            if ( sourceParameter.getType().isTypeVar() ) {
+                messager.printMessage( method, Message.RETRIEVAL_TYPE_VAR_SOURCE );
+                return false;
+            }
+        }
+
+        if ( returnType.isTypeVar() || resultType.isTypeVar() ) {
+                messager.printMessage( method, Message.RETRIEVAL_TYPE_VAR_RESULT );
+                return false;
+        }
+
         Type parameterType = sourceParameters.get( 0 ).getType();
 
         if ( parameterType.isIterableType() && !resultType.isIterableType() ) {
diff --git a/processor/src/test/java/org/mapstruct/ap/test/bugs/_631/Base1.java b/processor/src/test/java/org/mapstruct/ap/test/bugs/_631/Base1.java
new file mode 100644
index 000000000..247fd1a4d
--- /dev/null
+++ b/processor/src/test/java/org/mapstruct/ap/test/bugs/_631/Base1.java
@@ -0,0 +1,27 @@
+/**
+ *  Copyright 2012-2015 Gunnar Morling (http://www.gunnarmorling.de/)
+ *  and/or other contributors as indicated by the @authors tag. See the
+ *  copyright.txt file in the distribution for a full listing of all
+ *  contributors.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.mapstruct.ap.test.bugs._631;
+
+/**
+ *
+ * @author Sjaak Derksen
+ */
+public class Base1 {
+
+}
diff --git a/processor/src/test/java/org/mapstruct/ap/test/bugs/_631/Base2.java b/processor/src/test/java/org/mapstruct/ap/test/bugs/_631/Base2.java
new file mode 100644
index 000000000..085bb8df3
--- /dev/null
+++ b/processor/src/test/java/org/mapstruct/ap/test/bugs/_631/Base2.java
@@ -0,0 +1,27 @@
+/**
+ *  Copyright 2012-2015 Gunnar Morling (http://www.gunnarmorling.de/)
+ *  and/or other contributors as indicated by the @authors tag. See the
+ *  copyright.txt file in the distribution for a full listing of all
+ *  contributors.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.mapstruct.ap.test.bugs._631;
+
+/**
+ *
+ * @author Sjaak Derksen
+ */
+public class Base2 {
+
+}
diff --git a/processor/src/test/java/org/mapstruct/ap/test/bugs/_631/Issue631Test.java b/processor/src/test/java/org/mapstruct/ap/test/bugs/_631/Issue631Test.java
new file mode 100644
index 000000000..668f1c3d1
--- /dev/null
+++ b/processor/src/test/java/org/mapstruct/ap/test/bugs/_631/Issue631Test.java
@@ -0,0 +1,57 @@
+/**
+ *  Copyright 2012-2015 Gunnar Morling (http://www.gunnarmorling.de/)
+ *  and/or other contributors as indicated by the @authors tag. See the
+ *  copyright.txt file in the distribution for a full listing of all
+ *  contributors.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.mapstruct.ap.test.bugs._631;
+
+
+import javax.tools.Diagnostic.Kind;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mapstruct.ap.testutil.IssueKey;
+import org.mapstruct.ap.testutil.WithClasses;
+import org.mapstruct.ap.testutil.compilation.annotation.CompilationResult;
+import org.mapstruct.ap.testutil.compilation.annotation.Diagnostic;
+import org.mapstruct.ap.testutil.compilation.annotation.ExpectedCompilationOutcome;
+import org.mapstruct.ap.testutil.runner.AnnotationProcessorTestRunner;
+
+/**
+ * @author Sjaak Derksen
+ */
+@RunWith(AnnotationProcessorTestRunner.class)
+public class Issue631Test {
+
+    @Test
+    @IssueKey("631")
+    @ExpectedCompilationOutcome(
+        value = CompilationResult.FAILED,
+        diagnostics = {
+            @Diagnostic(type = SourceTargetMapper.class,
+                kind = Kind.ERROR,
+                line = 35,
+                messageRegExp = "Can't generate mapping method for a generic type variable target."),
+            @Diagnostic(type = SourceTargetMapper.class,
+                kind = Kind.ERROR,
+                line = 37,
+                messageRegExp = "Can't generate mapping method for a generic type variable source.")
+        }
+    )
+    @WithClasses({SourceTargetMapper.class, Base1.class, Base2.class})
+    public void showsCantMapPropertyError() {
+
+    }
+}
diff --git a/processor/src/test/java/org/mapstruct/ap/test/bugs/_631/SourceTargetMapper.java b/processor/src/test/java/org/mapstruct/ap/test/bugs/_631/SourceTargetMapper.java
new file mode 100644
index 000000000..6b5bc99a9
--- /dev/null
+++ b/processor/src/test/java/org/mapstruct/ap/test/bugs/_631/SourceTargetMapper.java
@@ -0,0 +1,38 @@
+/**
+ *  Copyright 2012-2015 Gunnar Morling (http://www.gunnarmorling.de/)
+ *  and/or other contributors as indicated by the @authors tag. See the
+ *  copyright.txt file in the distribution for a full listing of all
+ *  contributors.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.mapstruct.ap.test.bugs._631;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.factory.Mappers;
+
+/**
+ *
+ * @author Sjaak Derksen
+ * @param <X>
+ * @param <Y>
+ */
+@Mapper
+public interface SourceTargetMapper<X extends Base1, Y extends Base2> {
+
+    SourceTargetMapper INSTANCE = Mappers.getMapper( SourceTargetMapper.class );
+
+    X mapIntegerToBase1(Integer obj);
+
+    Integer mapBase2ToInteger(Y obj);
+}