diff --git a/Makefile b/Makefile
index 3bbe6c5..104220d 100644
--- a/Makefile
+++ b/Makefile
@@ -86,7 +86,7 @@ bedstead-bold-%.bdf.ps: bedstead
 	gs -q -P -dSAFER -dNODISPLAY -dBATCH $< > $@
 
 %.otf: %.ttx
-	ttx -o $@ $<
+	ttx --no-recalc-timestamp -o $@ $<
 
 %.png: %.ps $(OTFFILES) Fontmap
 	gs -P -q -dSAFER -sDEVICE=png16m -dTextAlphaBits=4 -o $@ $<