diff --git a/libs/gui/ConsumerBase.cpp b/libs/gui/ConsumerBase.cpp
index a1bdf4a..e7bc7dc 100644
--- a/libs/gui/ConsumerBase.cpp
+++ b/libs/gui/ConsumerBase.cpp
@@ -315,9 +315,10 @@
     if (!mSlots[slot].mFence.get()) {
         mSlots[slot].mFence = fence;
     } else {
+        char fenceName[32] = {};
+        snprintf(fenceName, 32, "%.28s:%d", mName.string(), slot);
         sp<Fence> mergedFence = Fence::merge(
-                String8::format("%.28s:%d", mName.string(), slot),
-                mSlots[slot].mFence, fence);
+                fenceName, mSlots[slot].mFence, fence);
         if (!mergedFence.get()) {
             CB_LOGE("failed to merge release fences");
             // synchronization is broken, the best we can do is hope fences