diff --git a/src/vim.h b/src/vim.h
index 30cf284..54d507e 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2736,4 +2736,7 @@
 // Maximum number of characters that can be fuzzy matched
 #define MAX_FUZZY_MATCHES	256
 
+// flags for equal_type()
+#define ETYPE_ARG_UNKNOWN 1
+
 #endif // VIM__H