diff --git a/src/language_server_api.h b/src/language_server_api.h
index 3e6b6ee9..36039d3b 100644
--- a/src/language_server_api.h
+++ b/src/language_server_api.h
@@ -11,6 +11,7 @@
 #include <variant.h>
 
 #include <algorithm>
+#include <iostream>
 #include <unordered_map>
 #include <unordered_set>