diff --git a/js/public/Value.h b/js/public/Value.h
index 01666ed4e..7c4f833e3 100644
--- a/js/public/Value.h
+++ b/js/public/Value.h
@@ -567,8 +567,11 @@ class MOZ_NON_PARAM alignas(8) Value
     }
 
     bool isMagic(JSWhyMagic why) const {
-        MOZ_ASSERT_IF(isMagic(), data.s.payload.why == why);
-        return isMagic();
+        if (!isMagic()) {
+            return false;
+        }
+        MOZ_RELEASE_ASSERT(data.s.payload.why == why);
+        return true;
     }
 
     JS::TraceKind traceKind() const {