diff --git a/Timeline.h b/Timeline.h
index d13b41d..a3194ca 100644
--- a/Timeline.h
+++ b/Timeline.h
@@ -100,7 +100,7 @@ public:
     inline GstClockTime last() const { return timing_.end - step_; }
     inline GstClockTime step() const { return step_; }
     inline GstClockTime duration() const { return timing_.duration(); }
-    inline size_t numFrames() const { return duration() / step_; }
+    inline size_t numFrames() const { if (step_) return duration() / step_; else return 1; }
     inline TimeInterval interval() const { return timing_; }
     GstClockTime next(GstClockTime time) const;
     GstClockTime previous(GstClockTime time) const;