diff --git a/plugins/sudoers/iolog.c b/plugins/sudoers/iolog.c
index 3a83d0781..976c49241 100644
--- a/plugins/sudoers/iolog.c
+++ b/plugins/sudoers/iolog.c
@@ -137,11 +137,12 @@ io_nextid(char *iolog_dir, char sessid[7])
 {
     struct stat sb;
     char buf[32], *ep;
-    int fd, i, ch;
+    int fd, i;
     unsigned long id = 0;
     int len;
     ssize_t nread;
     char pathbuf[PATH_MAX];
+    static const char b36char[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
 
     /*
      * Create I/O log directory if it doesn't already exist.
@@ -184,9 +185,8 @@ io_nextid(char *iolog_dir, char sessid[7])
      * Note that that least significant digits go at the end of the string.
      */
     for (i = 5; i >= 0; i--) {
-	ch = id % 36;
+	buf[i] = b36char[id % 36];
 	id /= 36;
-	buf[i] = ch < 10 ? ch + '0' : ch - 10 + 'A';
     }
     buf[6] = '\n';