1 files changed, 2 insertions, 2 deletions
diff --git a/Modules/binascii.c b/Modules/binascii.c
index 01e8860..19681b4 100644
--- a/Modules/binascii.c
+++ b/Modules/binascii.c
@@ -1102,8 +1102,8 @@ to_int(int c)
     if (isdigit(c))
         return c - '0';
     else {
-        if (isupper(c))
-            c = tolower(c);
+        if (Py_ISUPPER(c))
+            c = Py_TOLOWER(c);
         if (c >= 'a' && c <= 'f')
             return c - 'a' + 10;
     }