Include modsupport.h for getargs().
diff --git a/Objects/fileobject.c b/Objects/fileobject.c
index db9a088..e925b4d 100644
--- a/Objects/fileobject.c
+++ b/Objects/fileobject.c
@@ -25,6 +25,7 @@
 /* File object implementation */
 
 #include "allobjects.h"
+#include "modsupport.h"
 
 #define BUF(v) GETSTRINGVALUE((stringobject *)v)