diff --git a/libs/ui/Fence.cpp b/libs/ui/Fence.cpp
index 08340f2..932bcdd 100644
--- a/libs/ui/Fence.cpp
+++ b/libs/ui/Fence.cpp
@@ -63,6 +63,9 @@
 }
 
 int Fence::dup() const {
+    if (mFenceFd == -1) {
+        return -1;
+    }
     return ::dup(mFenceFd);
 }