diff --git a/samplecode/TransitionView.h b/samplecode/TransitionView.h
index ac95221..92e136a 100644
--- a/samplecode/TransitionView.h
+++ b/samplecode/TransitionView.h
@@ -12,4 +12,6 @@
 
 SkView* create_transition(SkView* prev, SkView* next, int direction);
 
+bool is_transition(SkView* view);
+
 #endif  // SAMPLECODE_TRANSITIONVIEW_H_