diff --git a/fastapi_cache/decorator.py b/fastapi_cache/decorator.py
index 091da3f..625b69c 100644
--- a/fastapi_cache/decorator.py
+++ b/fastapi_cache/decorator.py
@@ -116,24 +116,17 @@ def cache(
             key_builder = key_builder or FastAPICache.get_key_builder()
             backend = FastAPICache.get_backend()
 
-            if inspect.iscoroutinefunction(key_builder):
-                cache_key = await key_builder(
-                    func,
-                    namespace,
-                    request=request,
-                    response=response,
-                    args=args,
-                    kwargs=copy_kwargs,
-                )
-            else:
-                cache_key = key_builder(
-                    func,
-                    namespace,
-                    request=request,
-                    response=response,
-                    args=args,
-                    kwargs=copy_kwargs,
-                )
+            cache_key = key_builder(
+                func,
+                namespace,
+                request=request,
+                response=response,
+                args=args,
+                kwargs=copy_kwargs,
+            )
+            if inspect.isawaitable(cache_key):
+                cache_key = await cache_key
+
             try:
                 ttl, ret = await backend.get_with_ttl(cache_key)
             except Exception: