--- a/make.sh
+++ b/make.sh
@@ -19,6 +19,10 @@
 # public domain. The software is in the public domain and is
 # provided with absolutely no warranty. See the COPYING and CREDITS
 # files for more information.
+
+# Running make.sh with different options without clean.sh in the middle
+# can break things.
+sh clean.sh
 
 # If you're cross-compiling, make-config.sh should "do the right
 # thing" when run on the target machine, with the minor caveat that