diff --git a/libs/surfaceflinger_client/Surface.cpp b/libs/surfaceflinger_client/Surface.cpp
index 7af6ce8ba..c1e00ca68 100644
--- a/libs/surfaceflinger_client/Surface.cpp
+++ b/libs/surfaceflinger_client/Surface.cpp
@@ -1029,7 +1029,7 @@ int Surface::getBufferIndex(const sp<GraphicBuffer>& buffer) const
         // one of the buffers for which we do know the index.  This can happen
         // e.g. if GraphicBuffer is used to wrap an android_native_buffer_t that
         // was dequeued from an ANativeWindow.
-        for (int i = 0; i < mBuffers.size(); i++) {
+        for (size_t i = 0; i < mBuffers.size(); i++) {
             if (buffer->handle == mBuffers[i]->handle) {
                 idx = mBuffers[i]->getIndex();
                 break;