diff --git a/programs/cmd/builtins.c b/programs/cmd/builtins.c
index 33e96c1..af58717 100644
--- a/programs/cmd/builtins.c
+++ b/programs/cmd/builtins.c
@@ -2303,7 +2303,7 @@
       WCMD_output_asis (endBkt);
       WCMD_ReadFile (GetStdHandle(STD_INPUT_HANDLE), answer,
                      sizeof(answer)/sizeof(WCHAR), &count, NULL);
-      answer[0] = toupper(answer[0]);
+      answer[0] = toupperW(answer[0]);
     }
 
     /* Return the answer */