diff --git a/components/style/properties/gecko.mako.rs b/components/style/properties/gecko.mako.rs
index 2e2a55a16bb..3c4a45666b1 100644
--- a/components/style/properties/gecko.mako.rs
+++ b/components/style/properties/gecko.mako.rs
@@ -1204,7 +1204,6 @@ impl Clone for ${style_struct.gecko_struct_name} {
 
     # Types used with predefined_type()-defined properties that we can auto-generate.
     predefined_types = {
-        "length::NonNegativeLengthOrAuto": impl_style_coord,
         "length::NonNegativeLengthPercentageOrNormal": impl_style_coord,
         "Length": impl_absolute_length,
         "MozScriptMinSize": impl_absolute_length,