diff --git a/ui.c b/ui.c
index f74f3d3..37889fd 100644
--- a/ui.c
+++ b/ui.c
@@ -2465,7 +2465,7 @@ void regexp_error_popup(int rc, regex_t *pre)
 			popup_buffer[sizeof(popup_buffer) - 1] = 0x00;
 		}
 		else
-			strncat(popup_buffer, error, sizeof(popup_buffer));
+			strncat(popup_buffer, error, sizeof(popup_buffer) - sizeof(error));
 
 		myfree(error);
 	}