diff --git a/js/src/jsinterp.h b/js/src/jsinterp.h
index 6bd0db85ad91..467586c562e3 100644
--- a/js/src/jsinterp.h
+++ b/js/src/jsinterp.h
@@ -134,11 +134,7 @@ struct JSStackFrame {
 #endif
 
 #ifdef __cplusplus /* Aargh, LiveConnect, bug 442399. */
-    void assertValidStackDepth(uintN depth) {
-        extern jsval *StackBase(JSStackFrame *fp);
-        JS_ASSERT(0 <= regs->sp - StackBase(this));
-        JS_ASSERT(depth <= uintptr_t(regs->sp - StackBase(this)));
-    }
+    inline void assertValidStackDepth(uintN depth);
 #endif
 };
 
@@ -156,6 +152,15 @@ StackBase(JSStackFrame *fp)
     return fp->slots + fp->script->nfixed;
 }
 
+#ifdef __cplusplus /* Aargh, LiveConnect, bug 442399. */
+void
+JSStackFrame::assertValidStackDepth(uintN depth)
+{
+    JS_ASSERT(0 <= regs->sp - StackBase(this));
+    JS_ASSERT(depth <= uintptr_t(regs->sp - StackBase(this)));
+}
+#endif
+
 static JS_INLINE uintN
 GlobalVarCount(JSStackFrame *fp)
 {