diff --git a/src/vim.h b/src/vim.h
index 14630e6..67751ff 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2257,6 +2257,14 @@
     ESTACK_SCRIPT,
 } estack_arg_T;
 
+// Return value of match_keyprotocol()
+typedef enum {
+    KEYPROTOCOL_NONE,
+    KEYPROTOCOL_MOK2,
+    KEYPROTOCOL_KITTY,
+    KEYPROTOCOL_FAIL
+} keyprot_T;
+
 // Flags for assignment functions.
 #define ASSIGN_VAR	0     // ":var" (nothing special)
 #define ASSIGN_FINAL	0x01  // ":final"