--- a/servo/ports/geckolib/glue.rs
+++ b/servo/ports/geckolib/glue.rs
@@ -361,17 +361,17 @@ pub extern "C" fn Servo_AnimationCompose
         None
     };
 
     if need_underlying_value && underlying_value.is_none() {
         warn!("Underlying value should be valid when we expect to use it");
         return;
     }
 
-    // Temporaries used in the following if-block whose lifetimes we need to prlong.
+    // Temporaries used in the following if-block whose lifetimes we need to prolong.
     let raw_from_value;
     let from_composite_result;
     let from_value = if !segment.mFromValue.mServo.mRawPtr.is_null() {
         raw_from_value = unsafe { &*segment.mFromValue.mServo.mRawPtr };
         match segment.mFromComposite {
             CompositeOperation::Add => {
                 let value_to_composite = AnimationValue::as_arc(&raw_from_value).as_ref();
                 from_composite_result = underlying_value.as_ref().unwrap().add(value_to_composite);