diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 2a6a422331d0..3450c2af8da0 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -234,15 +234,25 @@ STRING_TO_JSVAL(JSString *str)
 #define JSVAL_INT_MAX           (JSVAL_INT_POW2(30) - 1)
 
 /* Not a function, because we have static asserts that use it */
-#define INT_FITS_IN_JSVAL(i)    ((jsuint)(i) - (jsuint)JSVAL_INT_MIN <=      \
+#define INT_FITS_IN_JSVAL(i)    ((jsuint)(i) - (jsuint)JSVAL_INT_MIN <=       \
                                  (jsuint)(JSVAL_INT_MAX - JSVAL_INT_MIN))
-/* Not a function, because we have static asserts that use it */
-/* FIXME:  Bug 506721, since that means we can't assert JSVAL_IS_INT(v) */
-#define JSVAL_TO_INT(v)         ((jsint)(v) >> 1)
+
+static JS_ALWAYS_INLINE jsint
+JSVAL_TO_INT(jsval v)
+{
+    JS_ASSERT(JSVAL_IS_INT(v));
+    return (jsint) v >> 1;
+}
 
 /* Not a function, because we have static asserts that use it */
-/* FIXME:  Bug 506721, since that means we can't assert INT_FITS_IN_JSVAL(i) */
-#define INT_TO_JSVAL(i)         (((jsval)(i) << 1) | JSVAL_INT)
+#define INT_TO_JSVAL_CONSTEXPR(i)  (((jsval)(i) << 1) | JSVAL_INT)
+
+static JS_ALWAYS_INLINE jsval
+INT_TO_JSVAL(jsint i)
+{
+    JS_ASSERT(INT_FITS_IN_JSVAL(i));
+    return INT_TO_JSVAL_CONSTEXPR(i);
+}
 
 /* Convert between boolean and jsval, asserting that inputs are valid. */
 static JS_ALWAYS_INLINE JSBool
diff --git a/js/src/jsfun.cpp b/js/src/jsfun.cpp
index 75ee312bfce7..9f6d5249db63 100644
--- a/js/src/jsfun.cpp
+++ b/js/src/jsfun.cpp
@@ -623,7 +623,7 @@ args_resolve(JSContext *cx, JSObject *obj, jsval idval, uintN flags,
             if (str == ATOM_TO_STRING(atom)) {
                 if (TEST_OVERRIDE_BIT(fp, ARGS_CALLEE))
                     return true;
-                v = INT_TO_JSVAL(fp->callee);
+                v = INT_TO_JSVAL(reinterpret_cast<jsint>(fp->callee));
             } else {
                 return true;
             }
diff --git a/js/src/jsinterp.cpp b/js/src/jsinterp.cpp
index 71e4e4ba1786..1aaa1df5fc7b 100644
--- a/js/src/jsinterp.cpp
+++ b/js/src/jsinterp.cpp
@@ -2436,8 +2436,8 @@ js_DumpOpMeters()
 #define CAN_DO_FAST_INC_DEC(v)     (((((v) << 1) ^ v) & 0x80000001) == 1)
 
 JS_STATIC_ASSERT(JSVAL_INT == 1);
-JS_STATIC_ASSERT(!CAN_DO_FAST_INC_DEC(INT_TO_JSVAL(JSVAL_INT_MIN)));
-JS_STATIC_ASSERT(!CAN_DO_FAST_INC_DEC(INT_TO_JSVAL(JSVAL_INT_MAX)));
+JS_STATIC_ASSERT(!CAN_DO_FAST_INC_DEC(INT_TO_JSVAL_CONSTEXPR(JSVAL_INT_MIN)));
+JS_STATIC_ASSERT(!CAN_DO_FAST_INC_DEC(INT_TO_JSVAL_CONSTEXPR(JSVAL_INT_MAX)));
 
 /*
  * Conditional assert to detect failure to clear a pending exception that is