diff --git a/src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/nodes/plugins/ffi/InterpreterProxy.java b/src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/nodes/plugins/ffi/InterpreterProxy.java
index 7151751ce..f6ab9c9dc 100644
--- a/src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/nodes/plugins/ffi/InterpreterProxy.java
+++ b/src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/nodes/plugins/ffi/InterpreterProxy.java
@@ -567,7 +567,7 @@ private long methodReturnInteger(final long integer) {
     private long methodReturnReceiver() {
         assert hasSucceeded();
         pop(numReceiverAndArguments - 1); // leave the receiver on the stack
-        return 0;
+        return 0L;
     }
 
     private long methodReturnString(final String string) {
@@ -579,7 +579,7 @@ private long methodReturnValue(final long oop) {
     }
 
     private long minorVersion() {
-        return 17;
+        return 17L;
     }
 
     private long nilObject() {
@@ -613,7 +613,7 @@ private long primitiveFail() {
         if (primFailCode == 0) {
             primitiveFailFor(1L);
         }
-        return returnNull();
+        return 0L;
     }
 
     private long primitiveFailFor(final long reasonCode) {