diff --git a/src/compiler/CompilerIR.h b/src/compiler/CompilerIR.h
index 953e3b1..6bda522 100644
--- a/src/compiler/CompilerIR.h
+++ b/src/compiler/CompilerIR.h
@@ -449,6 +449,8 @@
     kOpInvalid,
 } OpKind;
 
+std::ostream& operator<<(std::ostream& os, const OpKind& kind);
+
 typedef enum ConditionCode {
     kCondEq,
     kCondNe,