diff --git a/c/swap.h b/c/swap.h
index f24d2fe..e908bd3 100644
--- a/c/swap.h
+++ b/c/swap.h
@@ -1,5 +1,5 @@
 #include <stddef.h>
 
-void swap_loop(char* restrict a, char* restrict b, size_t len);
-void swap_malloc(char* restrict a, char* restrict b, size_t len);
-void swap_alloca(char* restrict a, char* restrict b, size_t len);
+void swap_loop(char* __restrict a, char* __restrict b, size_t len);
+void swap_malloc(char* __restrict a, char* __restrict b, size_t len);
+void swap_alloca(char* __restrict a, char* __restrict b, size_t len);