diff --git a/components/style/properties/declaration_block.rs b/components/style/properties/declaration_block.rs
index e192d08b22d..c88458d0fd9 100644
--- a/components/style/properties/declaration_block.rs
+++ b/components/style/properties/declaration_block.rs
@@ -564,23 +564,6 @@ impl PropertyDeclarationBlock {
         true
     }
 
-    /// Set the declaration importance for a given property, if found.
-    ///
-    /// Returns whether any declaration was updated.
-    pub fn set_importance(&mut self, property: &PropertyId, new_importance: Importance) -> bool {
-        let mut updated_at_least_one = false;
-        for (i, declaration) in self.declarations.iter().enumerate() {
-            if declaration.id().is_or_is_longhand_of(property) {
-                let is_important = new_importance.important();
-                if self.declarations_importance[i] != is_important {
-                    self.declarations_importance.set(i, is_important);
-                    updated_at_least_one = true;
-                }
-            }
-        }
-        updated_at_least_one
-    }
-
     /// <https://drafts.csswg.org/cssom/#dom-cssstyledeclaration-removeproperty>
     ///
     /// Returns whether any declaration was actually removed.