diff --git a/src/collections/sets.rs b/src/collections/sets.rs
index ee00c2983f8283ab04a7a4d5b75f277c238c7f87..a93d6f8df3c732fd08608df15a18535fe90e6ab2 100644
--- a/src/collections/sets.rs
+++ b/src/collections/sets.rs
@@ -72,15 +72,18 @@ impl<T: Eq> VecSet<T> {
         self.inner.pop()
     }
 
+    /// Pushes a new element into the set. Returns `false` if it was already
+    /// present and `true` if it is newly added.
     #[inline]
-    pub fn push(&mut self, to_push: T) {
+    pub fn push(&mut self, to_push: T) -> bool {
         for element in self.inner.iter() {
             if *element == to_push {
-                return;
+                return false;
             }
         }
 
         self.inner.push(to_push);
+        return true
     }
 
     #[inline]