diff --git a/Makefile b/Makefile
index 892a571c5..720c269af 100644
--- a/Makefile
+++ b/Makefile
@@ -101,7 +101,7 @@ makeinclude: configure configh.in makeinclude.in config.guess config.sub
 	touch config.h
 	chmod +x fltk-config
 
-configure: configure.in
+configure: configure.ac
 	autoconf
 
 config.guess config.sub:
diff --git a/configure.in b/configure.ac
similarity index 100%
rename from configure.in
rename to configure.ac