diff --git a/runtime/monitor.cc b/runtime/monitor.cc
index eb74fcf..f583167 100644
--- a/runtime/monitor.cc
+++ b/runtime/monitor.cc
@@ -771,7 +771,7 @@
         return false;
       }
       // Can't deflate if our lock count is too high.
-      if (monitor->lock_count_ > LockWord::kThinLockMaxCount) {
+      if (static_cast<uint32_t>(monitor->lock_count_) > LockWord::kThinLockMaxCount) {
         return false;
       }
       // Deflate to a thin lock.