diff -r 9eb74b221cff -r 2f0205599623 vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java
--- a/vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java	Sat Nov 17 17:43:15 2012 +0100
+++ b/vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java	Sat Nov 17 18:34:12 2012 +0100
@@ -93,7 +93,7 @@
         for (FieldData v : jc.getFields()) {
             if (!v.isStatic()) {
                 out.append("\n  this.fld_").
-                    append(v.getName()).append(" = 0;");
+                    append(v.getName()).append(initField(v));
             }
         }
         out.append("\n}\n\nfunction ").append(className).append("_proto() {");
@@ -844,7 +844,7 @@
     private void generateStaticField(FieldData v) throws IOException {
         out.append("\nvar ")
            .append(className(jc))
-           .append('_').append(v.getName()).append(" = 0;");
+           .append('_').append(v.getName()).append(initField(v));
     }
 
     private String findMethodName(MethodData m, StringBuilder cnt) {
@@ -1065,4 +1065,23 @@
         ap.parse(arr, cd);
         return found[0] ? values : null;
     }
+
+    private CharSequence initField(FieldData v) {
+        final String is = v.getInternalSig();
+        if (is.length() == 1) {
+            switch (is.charAt(0)) {
+                case 'S':
+                case 'J':
+                case 'B':
+                case 'Z':
+                case 'C':
+                case 'I': return " = 0;";
+                case 'F': 
+                case 'D': return " = 0.0";
+                default:
+                    throw new IllegalStateException(is);
+            }
+        }
+        return " = null;";
+    }
 }