X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?a=blobdiff_plain;f=singles.c;fp=singles.c;h=c20d0cf89c763f16bbd0fe231b2a80c384558b36;hb=0a9b0a7384e664126a3af418f047ef627c7ac279;hp=d8016ff21eb63c4737038d715e24857898e1c3c7;hpb=945d8f0a3a9bfe2702170a75484271c71931b2eb;p=sgt-puzzles.git

diff --git a/singles.c b/singles.c
index d8016ff..c20d0cf 100644
--- a/singles.c
+++ b/singles.c
@@ -324,7 +324,7 @@ static char n2c(int num) {
 }
 
 static int c2n(char c) {
-    if (isdigit(c))
+    if (isdigit((unsigned char)c))
         return (int)(c - '0');
     else if (c >= 'a' && c <= 'z')
         return (int)(c - 'a' + 10);