diff --git a/src/settings.rs b/src/settings.rs
index 2420a251..2781fbb1 100644
--- a/src/settings.rs
+++ b/src/settings.rs
@@ -75,10 +75,11 @@ impl Settings {
             displayed_attributes: None,
         }
     }
-    pub fn with_synonyms<S, U>(self, synonyms: HashMap<S, U>) -> Settings
+    pub fn with_synonyms<S, U, V>(self, synonyms: HashMap<S, U>) -> Settings
     where
         S: AsRef<str>,
-        U: IntoIterator<Item = S>,
+        V: AsRef<str>,
+        U: IntoIterator<Item = V>,
     {
         Settings {
             synonyms: Some(