--- a/dom/svg/nsSVGElement.cpp
+++ b/dom/svg/nsSVGElement.cpp
@@ -1232,18 +1232,19 @@ MappedAttrParser::ParseMappedAttrValue(n
       mParser.ParseProperty(propertyID, aMappedAttrValue, mDocURI, mBaseURI,
                             mElement->NodePrincipal(), mDecl->AsGecko(), &changed, false, true);
     } else {
       NS_ConvertUTF16toUTF8 value(aMappedAttrValue);
       // FIXME (bug 1343964): Figure out a better solution for sending the base uri to servo
       RefPtr<URLExtraData> data = new URLExtraData(mBaseURI, mDocURI,
                                                    mElement->NodePrincipal());
       // FIXME (bug 1342559): Set SVG parsing mode for lengths
-      changed = Servo_DeclarationBlock_SetPropertyById(mDecl->AsServo()->Raw(), propertyID,
-                                                       &value, false, data);
+      changed = Servo_DeclarationBlock_SetPropertyById(
+        mDecl->AsServo()->Raw(), propertyID, &value, false, data,
+        LengthParsingMode::SVG);
     }
 
     if (changed) {
       // The normal reporting of use counters by the nsCSSParser won't happen
       // since it doesn't have a sheet.
       if (nsCSSProps::IsShorthand(propertyID)) {
         CSSPROPS_FOR_SHORTHAND_SUBPROPERTIES(subprop, propertyID,
                                              CSSEnabledState::eForAllContent) {

--- a/layout/style/ServoBindingList.h
+++ b/layout/style/ServoBindingList.h
@@ -204,22 +204,24 @@ SERVO_BINDING_FUNC(Servo_DeclarationBloc
                    nsCSSPropertyID property, nsAString* value)
 SERVO_BINDING_FUNC(Servo_DeclarationBlock_GetPropertyIsImportant, bool,
                    RawServoDeclarationBlockBorrowed declarations,
                    const nsACString* property)
 SERVO_BINDING_FUNC(Servo_DeclarationBlock_SetProperty, bool,
                    RawServoDeclarationBlockBorrowed declarations,
                    const nsACString* property,
                    const nsACString* value, bool is_important,
-                   RawGeckoURLExtraData* data)
+                   RawGeckoURLExtraData* data,
+                   mozilla::LengthParsingMode length_parsing_mode)
 SERVO_BINDING_FUNC(Servo_DeclarationBlock_SetPropertyById, bool,
                    RawServoDeclarationBlockBorrowed declarations,
                    nsCSSPropertyID property,
                    const nsACString* value, bool is_important,
-                   RawGeckoURLExtraData* data)
+                   RawGeckoURLExtraData* data,
+                   mozilla::LengthParsingMode length_parsing_mode)
 SERVO_BINDING_FUNC(Servo_DeclarationBlock_RemoveProperty, void,
                    RawServoDeclarationBlockBorrowed declarations,
                    const nsACString* property)
 SERVO_BINDING_FUNC(Servo_DeclarationBlock_RemovePropertyById, void,
                    RawServoDeclarationBlockBorrowed declarations,
                    nsCSSPropertyID property)
 // Compose animation value for a given property.
 // |base_values| is nsRefPtrHashtable<nsUint32HashKey, RawServoAnimationValue>.

--- a/layout/style/nsDOMCSSDeclaration.cpp
+++ b/layout/style/nsDOMCSSDeclaration.cpp
@@ -347,17 +347,17 @@ nsDOMCSSDeclaration::ParsePropertyValue(
       nsCSSParser cssParser(env.mCSSLoader);
       cssParser.ParseProperty(aPropID, aPropValue,
                               env.mSheetURI, env.mBaseURI, env.mPrincipal,
                               decl, changed, aIsImportant);
     },
     [&](ServoDeclarationBlock* decl, URLExtraData* data) {
       NS_ConvertUTF16toUTF8 value(aPropValue);
       return Servo_DeclarationBlock_SetPropertyById(
-        decl->Raw(), aPropID, &value, aIsImportant, data);
+        decl->Raw(), aPropID, &value, aIsImportant, data, LengthParsingMode::Default);
     });
 }
 
 nsresult
 nsDOMCSSDeclaration::ParseCustomPropertyValue(const nsAString& aPropertyName,
                                               const nsAString& aPropValue,
                                               bool aIsImportant)
 {
@@ -369,17 +369,18 @@ nsDOMCSSDeclaration::ParseCustomProperty
       cssParser.ParseVariable(propName, aPropValue, env.mSheetURI,
                               env.mBaseURI, env.mPrincipal, decl,
                               changed, aIsImportant);
     },
     [&](ServoDeclarationBlock* decl, URLExtraData* data) {
       NS_ConvertUTF16toUTF8 property(aPropertyName);
       NS_ConvertUTF16toUTF8 value(aPropValue);
       return Servo_DeclarationBlock_SetProperty(
-        decl->Raw(), &property, &value, aIsImportant, data);
+        decl->Raw(), &property, &value, aIsImportant, data,
+        LengthParsingMode::Default);
     });
 }
 
 nsresult
 nsDOMCSSDeclaration::RemovePropertyInternal(nsCSSPropertyID aPropID)
 {
   DeclarationBlock* olddecl = GetCSSDeclaration(eOperation_RemoveProperty);
   if (!olddecl) {