diff --git a/src/vim.h b/src/vim.h
index dd571df..57866ef 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2506,7 +2506,9 @@
 #  define ELAPSED_INIT(v) v = GetTickCount()
 #  define ELAPSED_FUNC(v) elapsed(v)
 #  define ELAPSED_TYPE DWORD
-    long elapsed(DWORD start_tick);
+#   ifndef PROTO
+     long elapsed(DWORD start_tick);
+#   endif
 # endif
 #endif