diff --git a/Include/internal/pygetopt.h b/Include/internal/pygetopt.h
index df6f183..8ef2ada 100644
--- a/Include/internal/pygetopt.h
+++ b/Include/internal/pygetopt.h
@@ -1,11 +1,11 @@
 #ifndef Py_INTERNAL_PYGETOPT_H
 #define Py_INTERNAL_PYGETOPT_H
 
-int _PyOS_opterr;
-int _PyOS_optind;
-wchar_t *_PyOS_optarg;
+extern int _PyOS_opterr;
+extern int _PyOS_optind;
+extern wchar_t *_PyOS_optarg;
 
-void _PyOS_ResetGetOpt(void);
+extern void _PyOS_ResetGetOpt(void);
 
 typedef struct {
     const wchar_t *name;
@@ -13,7 +13,7 @@
     int val;
 } _PyOS_LongOption;
 
-int _PyOS_GetOpt(int argc, wchar_t **argv, wchar_t *optstring,
-                 const _PyOS_LongOption *longopts, int *longindex);
+extern int _PyOS_GetOpt(int argc, wchar_t **argv, wchar_t *optstring,
+                        const _PyOS_LongOption *longopts, int *longindex);
 
 #endif /* !Py_INTERNAL_PYGETOPT_H */