diff --git a/Make.rules.in b/Make.rules.in
index 24d34dbc0f3..9178904f629 100644
--- a/Make.rules.in
+++ b/Make.rules.in
@@ -182,7 +182,7 @@ LINTS  = $(C_SRCS:.c=.ln)
 	$(FONTFORGE) -script $(TOPSRCDIR)/fonts/genttf.ff $< $@
 
 .man.in.man:
-	sed -e 's,@bindir\@,$(bindir),g' -e 's,@dlldir\@,$(dlldir),g' -e 's,@PACKAGE_STRING\@,@PACKAGE_STRING@,g' $< >$@ || ($(RM) $@ && false)
+	LC_ALL=C sed -e 's,@bindir\@,$(bindir),g' -e 's,@dlldir\@,$(dlldir),g' -e 's,@PACKAGE_STRING\@,@PACKAGE_STRING@,g' $< >$@ || ($(RM) $@ && false)
 
 # 'all' target first in case the enclosing Makefile didn't define any target