diff --git a/gtk/gtkcssnumbervalue.c b/gtk/gtkcssnumbervalue.c
index f5e574c81d..83fa257f01 100644
--- a/gtk/gtkcssnumbervalue.c
+++ b/gtk/gtkcssnumbervalue.c
@@ -115,6 +115,15 @@ gtk_css_number_value_transition (GtkCssValue *start,
 {
   GtkCssValue *result, *mul_start, *mul_end;
 
+  if (progress == 0)
+    return _gtk_css_value_ref (start);
+
+  if (progress == 1)
+    return _gtk_css_value_ref (end);
+
+  if (start == end)
+    return _gtk_css_value_ref (start);
+
   mul_start = gtk_css_number_value_multiply (start, 1 - progress);
   mul_end = gtk_css_number_value_multiply (end, progress);