diff --git a/json-writer.h b/json-writer.h
index fc18acc7d91..83906b09c17 100644
--- a/json-writer.h
+++ b/json-writer.h
@@ -42,6 +42,8 @@
  * of the given strings.
  */
 
+#include "strbuf.h"
+
 struct json_writer
 {
 	/*