diff --git a/src/index.rs b/src/index.rs
index 68b1b6b..bdef615 100644
--- a/src/index.rs
+++ b/src/index.rs
@@ -98,6 +98,7 @@ impl InMemoryIndex {
     }
 
     /// True if this index contains no data.
+    #[inline]
     pub fn is_empty(&self) -> bool {
         self.word_count == 0
     }