diff --git a/src/built_ins.cpp b/src/built_ins.cpp
index d2dfa93..4bc4602 100644
--- a/src/built_ins.cpp
+++ b/src/built_ins.cpp
@@ -89,7 +89,7 @@ namespace Slime {
 #ifdef UNICODE
                 fullpath[0] = L'\0';
                 path_char* temp = char_to_path_char(Memory::get_c_str(file_name));
-                swprintf(fullpath, max_path_leno, L"%s%s", it, temp);
+                swprintf(fullpath, max_path_len, L"%s%s", it, temp);
                 free(temp);
 #else
                 fullpath[0] = '\0';