--- a/servo/components/style/properties/gecko.mako.rs
+++ b/servo/components/style/properties/gecko.mako.rs
@@ -5429,20 +5429,20 @@ clip-path
             },
             Either::Second(Auto) => NS_STYLE_COLUMN_COUNT_AUTO
         };
     }
 
     ${impl_simple_copy('column_count', 'mColumnCount')}
 
     pub fn clone_column_count(&self) -> longhands::column_count::computed_value::T {
-        use gecko_bindings::structs::NS_STYLE_COLUMN_COUNT_AUTO;
+        use gecko_bindings::structs::{NS_STYLE_COLUMN_COUNT_AUTO, nsStyleColumn_kMaxColumnCount};
         if self.gecko.mColumnCount != NS_STYLE_COLUMN_COUNT_AUTO {
-            debug_assert!((self.gecko.mColumnCount as i32) >= 0 &&
-                          (self.gecko.mColumnCount as i32) < i32::max_value());
+            debug_assert!(self.gecko.mColumnCount >= 1 &&
+                          self.gecko.mColumnCount <= nsStyleColumn_kMaxColumnCount);
             Either::First((self.gecko.mColumnCount as i32).into())
         } else {
             Either::Second(Auto)
         }
     }
 
     <% impl_non_negative_app_units("column_rule_width", "mColumnRuleWidth", need_clone=True,
                                    round_to_pixels=True) %>