diff --git a/src/structs.h b/src/structs.h
index 5331183..265fe02 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -4438,7 +4438,10 @@
 
 // Struct used to pass to error messages about where the error happened.
 typedef struct {
+    char    *wt_func_name;  // function name or NULL
     char    wt_index;	    // argument or variable index, 0 means unknown
     char    wt_variable;    // "variable" when TRUE, "argument" otherwise
 } where_T;
 
+#define WHERE_INIT {NULL, 0, 0}
+