Make new gcc -Wall happy
diff --git a/Modules/structmodule.c b/Modules/structmodule.c
index 065ec6f..0cf996f 100644
--- a/Modules/structmodule.c
+++ b/Modules/structmodule.c
@@ -1008,7 +1008,7 @@
 	s = fmt;
 	size = 0;
 	while ((c = *s++) != '\0') {
-		if (isspace(c))
+		if (isspace((int)c))
 			continue;
 		if ('0' <= c && c <= '9') {
 			num = c - '0';
@@ -1110,7 +1110,7 @@
 	res = restart = PyString_AsString(result);
 
 	while ((c = *s++) != '\0') {
-		if (isspace(c))
+		if (isspace((int)c))
 			continue;
 		if ('0' <= c && c <= '9') {
 			num = c - '0';
@@ -1242,7 +1242,7 @@
 	str = start;
 	s = fmt;
 	while ((c = *s++) != '\0') {
-		if (isspace(c))
+		if (isspace((int)c))
 			continue;
 		if ('0' <= c && c <= '9') {
 			num = c - '0';