diff --git a/components/style/properties/helpers/animated_properties.mako.rs b/components/style/properties/helpers/animated_properties.mako.rs
index 17c10809afc..4b734167c7a 100644
--- a/components/style/properties/helpers/animated_properties.mako.rs
+++ b/components/style/properties/helpers/animated_properties.mako.rs
@@ -2274,7 +2274,7 @@ impl Animatable for MatrixDecomposed3D {
         use std::f64;
 
         debug_assert!((self_portion + other_portion - 1.0f64).abs() <= f64::EPSILON ||
-                      other_portion == 1.0f64,
+                      other_portion == 1.0f64 || other_portion == 0.0f64,
                       "add_weighted should only be used for interpolating or accumulating transforms");
 
         let mut sum = *self;