diff --git a/src/Init/Data/Ord/String.lean b/src/Init/Data/Ord/String.lean
index 37c46be239..3e409e970a 100644
--- a/src/Init/Data/Ord/String.lean
+++ b/src/Init/Data/Ord/String.lean
@@ -28,6 +28,7 @@ namespace String
 /--
 Lexicographic comparison of strings
 -/
+@[extern "lean_string_compare"]
 def compare (s₁ s₂ : @& String) : Ordering :=
   compareOfLessAndEq s₁ s₂