diff --git a/js/src/builtin/TestingFunctions.cpp b/js/src/builtin/TestingFunctions.cpp
index 3d31c595f19b..d58f6fdca663 100644
--- a/js/src/builtin/TestingFunctions.cpp
+++ b/js/src/builtin/TestingFunctions.cpp
@@ -3979,7 +3979,15 @@ GetModuleEnvironmentValue(JSContext* cx, unsigned argc, Value* vp)
     if (!JS_StringToId(cx, name, &id))
         return false;
 
-    return GetProperty(cx, env, env, id, args.rval());
+    if (!GetProperty(cx, env, env, id, args.rval()))
+        return false;
+
+    if (args.rval().isMagic(JS_UNINITIALIZED_LEXICAL)) {
+        ReportRuntimeLexicalError(cx, JSMSG_UNINITIALIZED_LEXICAL, id);
+        return false;
+    }
+
+    return true;
 }
 
 #ifdef DEBUG
diff --git a/js/src/jit-test/tests/modules/bug1394493.js b/js/src/jit-test/tests/modules/bug1394493.js
new file mode 100644
index 000000000000..1fc189960285
--- /dev/null
+++ b/js/src/jit-test/tests/modules/bug1394493.js
@@ -0,0 +1,4 @@
+// |jit-test| error: ReferenceError
+
+let m = parseModule("export let r = y; y = 4;");
+getModuleEnvironmentValue(m, "r").toString()