diff --git a/src/de.hpi.swa.trufflesqueak.ffi.native/src/InterpreterProxy.c b/src/de.hpi.swa.trufflesqueak.ffi.native/src/InterpreterProxy.c
index 0f71bf6d2..54a4474a1 100644
--- a/src/de.hpi.swa.trufflesqueak.ffi.native/src/InterpreterProxy.c
+++ b/src/de.hpi.swa.trufflesqueak.ffi.native/src/InterpreterProxy.c
@@ -70,6 +70,7 @@ VirtualMachine* createInterpreterProxy(
 	sqInt (*popthenPush)(sqInt nItems, sqInt oop),
 	sqInt (*positive32BitIntegerFor)(unsigned int integerValue),
 	usqInt (*positive32BitValueOf)(sqInt oop),
+	sqInt (*positive64BitIntegerFor)(usqLong integerValue),
 	usqLong (*positive64BitValueOf)(sqInt oop),
 	sqInt (*primitiveFail)(void),
 	sqInt (*primitiveFailFor)(sqInt reasonCode),
@@ -147,6 +148,7 @@ VirtualMachine* createInterpreterProxy(
 	interpreterProxy->popthenPush = popthenPush;
 	interpreterProxy->positive32BitIntegerFor = positive32BitIntegerFor;
 	interpreterProxy->positive32BitValueOf = positive32BitValueOf;
+	interpreterProxy->positive64BitIntegerFor = positive64BitIntegerFor;
 	interpreterProxy->positive64BitValueOf = positive64BitValueOf;
 	interpreterProxy->primitiveFail = primitiveFail;
 	interpreterProxy->primitiveFailFor = primitiveFailFor;
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 b93623395..eeeac92af 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
@@ -148,6 +148,7 @@ private TruffleExecutable[] getExecutables() {
                         TruffleExecutable.wrap("(SINT64,SINT64):SINT64", this::popthenPush),
                         TruffleExecutable.wrap("(UINT64):SINT64", this::positive32BitIntegerFor),
                         TruffleExecutable.wrap("(SINT64):UINT64", this::positive32BitValueOf),
+                        TruffleExecutable.wrap("(SINT64):UINT64", this::positive64BitIntegerFor),
                         TruffleExecutable.wrap("(SINT64):UINT64", this::positive64BitValueOf),
                         TruffleExecutable.wrap("():SINT64", this::primitiveFail),
                         TruffleExecutable.wrap("(SINT64):SINT64", this::primitiveFailFor),
@@ -651,6 +652,10 @@ private long positive32BitValueOf(final long oop) {
         return integerValueOf(oop) & Integer.MAX_VALUE;
     }
 
+    private long positive64BitIntegerFor(final long integerValue) {
+        return integerObjectOf(Math.abs(integerValue));
+    }
+
     private long positive64BitValueOf(final long oop) {
         return Math.abs(integerValueOf(oop));
     }