diff --git a/src/makewat.env b/src/makewat.env
index 24acfc30ac..2c60ca773f 100644
--- a/src/makewat.env
+++ b/src/makewat.env
@@ -33,6 +33,8 @@ WATCOM_SUFFIX=_w
 WINVERFLAGS = /dWINVER=0x400 /d_WIN32_IE=0x0300
 
 # optimize for space/time: /os or /ot
+#
+# NB: at least with OpenWatcom 1.0 using /ox leads to buggy code, don't use it
 !ifeq FINAL 1
 OPTFLAGS=/oails /5r
 !else