diff --git a/adb/adb.c b/adb/adb.c
index f4ee448..229f3ef 100644
--- a/adb/adb.c
+++ b/adb/adb.c
@@ -1067,7 +1067,7 @@
 
     strncpy(hostbuf, host, sizeof(hostbuf) - 1);
     if (portstr) {
-        if (portstr - host >= sizeof(hostbuf)) {
+        if ((unsigned int)(portstr - host) >= sizeof(hostbuf)) {
             snprintf(buffer, buffer_size, "bad host name %s", host);
             return;
         }