--- a/debug.c
+++ b/debug.c
@@ -153,7 +153,7 @@ void debug_logit(uint8_t level, const ch
 
     if (debug_tid) {
         tidbuf = malloc((3*sizeof(pthread_t)+5)+strlen(format));
-        sprintf(tidbuf, "(%ld) %s", pthread_self(), format);
+        sprintf(tidbuf, "(%ld) %s", (long int)pthread_self(), format);
         format = tidbuf;
     } else
         tidbuf = NULL;