diff --git a/adb/daemon/mdns.cpp b/adb/daemon/mdns.cpp
index fa692c0..c1e766e 100644
--- a/adb/daemon/mdns.cpp
+++ b/adb/daemon/mdns.cpp
@@ -150,11 +150,11 @@
     for (size_t i = 0; i < len; ++i) {
         uint8_t val = dist(mt);
         if (val < 10) {
-            ret += '0' + val;
+            ret += static_cast<char>('0' + val);
         } else if (val < 36) {
-            ret += 'A' + (val - 10);
+            ret += static_cast<char>('A' + (val - 10));
         } else {
-            ret += 'a' + (val - 36);
+            ret += static_cast<char>('a' + (val - 36));
         }
     }
     return ret;