diff --git a/host-utils.h b/host-utils.h
index e335c5cb68..0ddc176582 100644
--- a/host-utils.h
+++ b/host-utils.h
@@ -164,7 +164,7 @@ static inline int ctz64(uint64_t val)
 {
 #if QEMU_GNUC_PREREQ(3, 4)
     if (val)
-        return __builtin_ctz(val);
+        return __builtin_ctzll(val);
     else
         return 64;
 #else