diff --git a/Doc/ext/ext.tex b/Doc/ext/ext.tex
index 83f468182eb..203514923c1 100644
--- a/Doc/ext/ext.tex
+++ b/Doc/ext/ext.tex
@@ -1603,7 +1603,7 @@ extern "C" {
 /* C API functions */
 #define PySpam_System_NUM 0
 #define PySpam_System_RETURN int
-#define PySpam_System_PROTO Py_PROTO((char *command))
+#define PySpam_System_PROTO(char *command)
 
 /* Total number of C API pointers */
 #define PySpam_API_pointers 1