diff --git a/src/transcript/transcript-drawing-area.vala b/src/transcript/transcript-drawing-area.vala
index 883de0a..e100d27 100644
--- a/src/transcript/transcript-drawing-area.vala
+++ b/src/transcript/transcript-drawing-area.vala
@@ -273,6 +273,9 @@ private class ChatItemAnimation
     private double duration = 0.0;
     private Gdk.FrameClock frame_clock = null;
 
+    delegate double EaseFunction(double t);
+    private EaseFunction ease_function = ease_out_quart;
+
     public ChatItemAnimation(Gdk.FrameClock frame_clock) {
         this.frame_clock = frame_clock;
         progress = 0.0f;
@@ -285,7 +288,9 @@ private class ChatItemAnimation
     }
 
     public void tick_animation() {
-        progress = ease_out_quart((frame_clock.get_frame_time() - start_time) / (duration * 1000000.0));
+        double t = (frame_clock.get_frame_time() - start_time) / (duration * 1000000.0);
+        t = double.min(1.0, double.max(0.0, t));
+        progress = ease_function(t);
     }
 
     private static double ease_out_quart(double t) {