diff --git a/WDL/_util.py b/WDL/_util.py
index 1affe49a..c7be2ffb 100644
--- a/WDL/_util.py
+++ b/WDL/_util.py
@@ -32,11 +32,13 @@
 from types import FrameType
 from pythonjsonlogger import jsonlogger
 
+T = TypeVar("T")
+
 __all__: List[str] = []
 
 
-def export(obj) -> str:  # pyre-ignore
-    __all__.append(obj.__name__)
+def export(obj: T) -> T:
+    __all__.append(obj.__name__)  # pyre-ignore
     return obj
 
 
@@ -67,9 +69,6 @@ def strip_leading_whitespace(txt: str) -> Tuple[int, str]:
     return (to_strip, "\n".join(lines))
 
 
-T = TypeVar("T")
-
-
 @export
 class AdjM(Generic[T]):
     # A sparse adjacency matrix for topological sorting