fix spelling
diff --git a/src/lib.rs b/src/lib.rs
index 144e966..1221361 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -753,7 +753,7 @@
         self.helper.as_mut()
     }
 
-    /// Return an imutable reference to the helper.
+    /// Return an immutable reference to the helper.
     pub fn get_helper_const(&self) -> Option<&H> {
         self.helper.as_ref()
     }