diff --git a/fastapi_cache/decorator.py b/fastapi_cache/decorator.py
index d24c565..b203bb3 100644
--- a/fastapi_cache/decorator.py
+++ b/fastapi_cache/decorator.py
@@ -66,11 +66,15 @@ def cache(
             async def ensure_async_func(*args, **kwargs):
                 """Run cached sync functions in thread pool just like FastAPI."""
                 if inspect.iscoroutinefunction(func):
-                    # async, return as is
-                    return func(*args, **kwargs)
+                    # async, return as is.
+                    # unintuitively, we have to await once here, so that caller
+                    # does not have to await twice. See
+                    # https://stackoverflow.com/a/59268198/532513
+                    return await func(*args, **kwargs)
                 else:
                     # sync, wrap in thread and return async
-                    return run_in_threadpool(func, *args, **kwargs)
+                    # see above why we have to await even although caller also awaits.
+                    return await run_in_threadpool(func, *args, **kwargs)
 
 
             copy_kwargs = kwargs.copy()