diff --git a/packages/core/src/render3/jit/injectable.ts b/packages/core/src/render3/jit/injectable.ts
index 0e77c9a3f5..64a218d3a0 100644
--- a/packages/core/src/render3/jit/injectable.ts
+++ b/packages/core/src/render3/jit/injectable.ts
@@ -27,6 +27,10 @@ export function compileInjectable(type: Type<any>, srcMeta?: Injectable): void {
   const meta: Injectable = srcMeta || {providedIn: null};
 
   let def: any = null;
+
+  // if NG_INJECTABLE_DEF is already defined on this class then don't overwrite it
+  if (type.hasOwnProperty(NG_INJECTABLE_DEF)) return;
+
   Object.defineProperty(type, NG_INJECTABLE_DEF, {
     get: () => {
       if (def === null) {