diff --git a/src/charset.c b/src/charset.c
index bda3f91..0e4dbbe 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -1958,7 +1958,7 @@
 	if (enc_latin1like)
 	    return (latin1flags[c] & LATIN1LOWER) == LATIN1LOWER;
     }
-    return islower(c);
+    return SAFE_islower(c);
 }
 
     int
@@ -1982,7 +1982,7 @@
 	if (enc_latin1like)
 	    return (latin1flags[c] & LATIN1UPPER) == LATIN1UPPER;
     }
-    return isupper(c);
+    return SAFE_isupper(c);
 }
 
     int