diff --git a/Makefile b/Makefile
index 737db18..ec14bd2 100644
--- a/Makefile
+++ b/Makefile
@@ -43,7 +43,7 @@ clean-all:
 .SUFFIXES: .nr .html .html .c .o
 
 .nr.html:
-	cat $< | nulldoc > $@
+	cat $< | nlroff > $@
 
 .c.o:
 	$(CC) $(CFLAGS) $< -c -o $@