--- a/servo/components/style/properties/helpers/animated_properties.mako.rs
+++ b/servo/components/style/properties/helpers/animated_properties.mako.rs
@@ -1687,18 +1687,18 @@ fn decompose_3d_matrix(mut matrix: Compu
 fn decompose_2d_matrix(matrix: &ComputedMatrix) -> Result<MatrixDecomposed3D, ()> {
     // The index is column-major, so the equivalent transform matrix is:
     // | m11 m21  0 m41 |  =>  | m11 m21 | and translate(m41, m42)
     // | m12 m22  0 m42 |      | m12 m22 |
     // |   0   0  1   0 |
     // |   0   0  0   1 |
     let (mut m11, mut m12) = (matrix.m11, matrix.m12);
     let (mut m21, mut m22) = (matrix.m21, matrix.m22);
+    // Check if this is a singular matrix.
     if m11 * m22 == m12 * m21 {
-        // singular matrix
         return Err(());
     }
 
     let mut scale_x = (m11 * m11 + m12 * m12).sqrt();
     m11 /= scale_x;
     m12 /= scale_x;
 
     let mut shear_xy = m11 * m21 + m12 * m22;
@@ -1706,18 +1706,20 @@ fn decompose_2d_matrix(matrix: &Computed
     m22 -= m12 * shear_xy;
 
     let scale_y = (m21 * m21 + m22 * m22).sqrt();
     m21 /= scale_y;
     m22 /= scale_y;
     shear_xy /= scale_y;
 
     let determinant = m11 * m22 - m12 * m21;
-    debug_assert!(0.99 < determinant.abs() && determinant.abs() < 1.01,
-                  "determinant should now be 1 or -1");
+    // Determinant should now be 1 or -1.
+    if 0.99 > determinant.abs() || determinant.abs() > 1.01 {
+        return Err(());
+    }
 
     if determinant < 0. {
         m11 = -m11;
         m12 = -m12;
         shear_xy = -shear_xy;
         scale_x = -scale_x;
     }