diff --git a/components/style/binding_tools/regen.py b/components/style/binding_tools/regen.py
index 1c7e193fa13..62f5a719daf 100755
--- a/components/style/binding_tools/regen.py
+++ b/components/style/binding_tools/regen.py
@@ -277,7 +277,6 @@ COMPILATION_TARGETS = {
             "StyleBasicShape",
             "StyleBasicShapeType",
             "StyleClipPath",
-            "nscoord",
             "nsCSSKeyword",
             "nsCSSShadowArray",
             "nsCSSValue",
@@ -331,6 +330,8 @@ COMPILATION_TARGETS = {
             "nsStyleVariables",
             "nsStyleVisibility",
             "nsStyleXUL",
+            "nscoord",
+            "nsresult",
         ],
         "array_types": {
             "uintptr_t": "usize",
diff --git a/components/style/gecko/conversions.rs b/components/style/gecko/conversions.rs
index 89a53fdd697..e32168a436d 100644
--- a/components/style/gecko/conversions.rs
+++ b/components/style/gecko/conversions.rs
@@ -14,11 +14,12 @@ use gecko_bindings::bindings::{Gecko_CreateGradient, Gecko_SetGradientImageValue
 use gecko_bindings::bindings::{RawServoStyleSheet, RawServoDeclarationBlock, RawServoStyleRule};
 use gecko_bindings::bindings::{ServoComputedValues, ServoCssRules};
 use gecko_bindings::structs::{nsStyleCoord_CalcValue, nsStyleImage};
+use gecko_bindings::structs::nsresult;
 use gecko_bindings::sugar::ns_style_coord::{CoordDataValue, CoordDataMut};
 use gecko_bindings::sugar::ownership::{HasArcFFI, HasFFI};
 use parking_lot::RwLock;
 use properties::{ComputedValues, PropertyDeclarationBlock};
-use stylesheets::{CssRules, Stylesheet, StyleRule};
+use stylesheets::{CssRules, RulesMutateError, Stylesheet, StyleRule};
 use values::computed::{CalcLengthOrPercentage, Gradient, Image, LengthOrPercentage, LengthOrPercentageOrAuto};
 
 unsafe impl HasFFI for Stylesheet {
@@ -497,3 +498,14 @@ pub mod basic_shape {
         }
     }
 }
+
+impl From<RulesMutateError> for nsresult {
+    fn from(other: RulesMutateError) -> Self {
+        match other {
+            RulesMutateError::Syntax => nsresult::NS_ERROR_DOM_SYNTAX_ERR,
+            RulesMutateError::IndexSize => nsresult::NS_ERROR_DOM_INDEX_SIZE_ERR,
+            RulesMutateError::HierarchyRequest => nsresult::NS_ERROR_DOM_HIERARCHY_REQUEST_ERR,
+            RulesMutateError::InvalidState => nsresult::NS_ERROR_DOM_INVALID_STATE_ERR,
+        }
+    }
+}
diff --git a/components/style/gecko_bindings/bindings.rs b/components/style/gecko_bindings/bindings.rs
index de034c92460..fb290136855 100644
--- a/components/style/gecko_bindings/bindings.rs
+++ b/components/style/gecko_bindings/bindings.rs
@@ -71,7 +71,6 @@ use gecko_bindings::structs::SheetParsingMode;
 use gecko_bindings::structs::StyleBasicShape;
 use gecko_bindings::structs::StyleBasicShapeType;
 use gecko_bindings::structs::StyleClipPath;
-use gecko_bindings::structs::nscoord;
 use gecko_bindings::structs::nsCSSKeyword;
 use gecko_bindings::structs::nsCSSShadowArray;
 use gecko_bindings::structs::nsCSSValue;
@@ -200,6 +199,8 @@ unsafe impl Sync for nsStyleVisibility {}
 use gecko_bindings::structs::nsStyleXUL;
 unsafe impl Send for nsStyleXUL {}
 unsafe impl Sync for nsStyleXUL {}
+use gecko_bindings::structs::nscoord;
+use gecko_bindings::structs::nsresult;
 
 #[repr(i32)]
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
@@ -1025,6 +1026,17 @@ extern "C" {
                                          index: u32)
      -> RawServoStyleRuleStrong;
 }
+extern "C" {
+    pub fn Servo_CssRules_InsertRule(rules: ServoCssRulesBorrowed,
+                                     sheet: RawServoStyleSheetBorrowed,
+                                     rule: *const nsACString_internal,
+                                     index: u32, nested: bool,
+                                     rule_type: *mut u16) -> nsresult;
+}
+extern "C" {
+    pub fn Servo_CssRules_DeleteRule(rules: ServoCssRulesBorrowed, index: u32)
+     -> nsresult;
+}
 extern "C" {
     pub fn Servo_StyleRule_Debug(rule: RawServoStyleRuleBorrowed,
                                  result: *mut nsACString_internal);
diff --git a/ports/geckolib/glue.rs b/ports/geckolib/glue.rs
index deed07b856d..3043f879e64 100644
--- a/ports/geckolib/glue.rs
+++ b/ports/geckolib/glue.rs
@@ -43,6 +43,7 @@ use style::gecko_bindings::bindings::nsTArrayBorrowed_uintptr_t;
 use style::gecko_bindings::structs;
 use style::gecko_bindings::structs::{SheetParsingMode, nsIAtom};
 use style::gecko_bindings::structs::{nsRestyleHint, nsChangeHint};
+use style::gecko_bindings::structs::nsresult;
 use style::gecko_bindings::sugar::ownership::{FFIArcHelpers, HasArcFFI, HasBoxFFI};
 use style::gecko_bindings::sugar::ownership::{HasSimpleFFI, Strong};
 use style::gecko_bindings::sugar::refptr::{GeckoArcPrincipal, GeckoArcURI};
@@ -332,6 +333,31 @@ pub extern "C" fn Servo_CssRules_GetStyleRuleAt(rules: ServoCssRulesBorrowed, in
     }
 }
 
+#[no_mangle]
+pub extern "C" fn Servo_CssRules_InsertRule(rules: ServoCssRulesBorrowed, sheet: RawServoStyleSheetBorrowed,
+                                            rule: *const nsACString, index: u32, nested: bool,
+                                            rule_type: *mut u16) -> nsresult {
+    let rules = RwLock::<CssRules>::as_arc(&rules);
+    let sheet = Stylesheet::as_arc(&sheet);
+    let rule = unsafe { rule.as_ref().unwrap().as_str_unchecked() };
+    match rules.write().insert_rule(rule, sheet, index as usize, nested) {
+        Ok(new_rule) => {
+            *unsafe { rule_type.as_mut().unwrap() } = new_rule.rule_type() as u16;
+            nsresult::NS_OK
+        }
+        Err(err) => err.into()
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn Servo_CssRules_DeleteRule(rules: ServoCssRulesBorrowed, index: u32) -> nsresult {
+    let rules = RwLock::<CssRules>::as_arc(&rules);
+    match rules.write().remove_rule(index as usize) {
+        Ok(_) => nsresult::NS_OK,
+        Err(err) => err.into()
+    }
+}
+
 #[no_mangle]
 pub extern "C" fn Servo_CssRules_AddRef(rules: ServoCssRulesBorrowed) -> () {
     unsafe { RwLock::<CssRules>::addref(rules) };