diff --git a/src/com/sun/jna/Function.java b/src/com/sun/jna/Function.java
index a4fd26ff8..521725f2a 100644
--- a/src/com/sun/jna/Function.java
+++ b/src/com/sun/jna/Function.java
@@ -418,7 +418,7 @@ Object invoke(Object[] args, Class<?> returnType, boolean allowObjects, int fixe
             Native.invokeVoid(this, this.peer, callFlags, args);
             result = null;
         } else if (returnType==boolean.class || returnType==Boolean.class) {
-            result = valueOf(Native.invokeInt(this, this.peer, callFlags, args) != 0);
+            result = valueOf((byte)Native.invokeInt(this, this.peer, callFlags, args) != 0);
         } else if (returnType==byte.class || returnType==Byte.class) {
             result = Byte.valueOf((byte)Native.invokeInt(this, this.peer, callFlags, args));
         } else if (returnType==short.class || returnType==Short.class) {