diff --git a/env_universal_common.cpp b/env_universal_common.cpp
index dbf79c1a6..c175b4a14 100644
--- a/env_universal_common.cpp
+++ b/env_universal_common.cpp
@@ -756,8 +756,9 @@ static wcstring full_escape(const wchar_t *in)
         {
             out.push_back(c);
         }
-        else if (c < 256)
+        else if (c <= ASCII_MAX)
         {
+            // See #1225 for discussion of use of ASCII_MAX here
             append_format(out, L"\\x%.2x", c);
         }
         else if (c < 65536)