diff --git a/Include/patchlevel.h b/Include/patchlevel.h
index 334478d71ea..83165a25c53 100644
--- a/Include/patchlevel.h
+++ b/Include/patchlevel.h
@@ -2,7 +2,7 @@
 /* Python version identification scheme.
 
    When the major or minor version changes, the VERSION variable in
-   configure.in must also be changed.
+   configure.ac must also be changed.
 
    There is also (independent) API version information in modsupport.h.
 */
diff --git a/Makefile.pre.in b/Makefile.pre.in
index 3008d6d73ad..a85f8ddf1cb 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -161,7 +161,7 @@ SRCDIRS= 	@SRCDIRS@
 SUBDIRSTOO=	Include Lib Misc
 
 # Files and directories to be distributed
-CONFIGFILES=	configure configure.in acconfig.h pyconfig.h.in Makefile.pre.in
+CONFIGFILES=	configure configure.ac acconfig.h pyconfig.h.in Makefile.pre.in
 DISTFILES=	README ChangeLog $(CONFIGFILES)
 DISTDIRS=	$(SUBDIRS) $(SUBDIRSTOO) Ext-dummy
 DIST=		$(DISTFILES) $(DISTDIRS)
@@ -1210,7 +1210,7 @@ recheck:
 	$(SHELL) config.status --recheck
 	$(SHELL) config.status
 
-# Rebuild the configure script from configure.in; also rebuild pyconfig.h.in
+# Rebuild the configure script from configure.ac; also rebuild pyconfig.h.in
 autoconf:
 	(cd $(srcdir); autoconf -Wall)
 	(cd $(srcdir); autoheader -Wall)
diff --git a/PC/pyconfig.h b/PC/pyconfig.h
index 138d8fa7b21..ba80800857b 100644
--- a/PC/pyconfig.h
+++ b/PC/pyconfig.h
@@ -340,7 +340,7 @@ Py_NO_ENABLE_SHARED to find out.  Also support MS_NO_COREDLL for b/w compat */
 #	define SIZEOF_FPOS_T 8
 #	define SIZEOF_HKEY 8
 #	define SIZEOF_SIZE_T 8
-/* configure.in defines HAVE_LARGEFILE_SUPPORT iff HAVE_LONG_LONG,
+/* configure.ac defines HAVE_LARGEFILE_SUPPORT iff HAVE_LONG_LONG,
    sizeof(off_t) > sizeof(long), and sizeof(PY_LONG_LONG) >= sizeof(off_t).
    On Win64 the second condition is not true, but if fpos_t replaces off_t
    then this is true. The uses of HAVE_LARGEFILE_SUPPORT imply that Win64
diff --git a/configure b/configure
index 5f00c1ecfaf..9e7cfc06b2c 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.in Revision.
+# From configure.ac Revision.
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.68 for python 3.2.
 #
diff --git a/configure.in b/configure.ac
similarity index 100%
rename from configure.in
rename to configure.ac
diff --git a/pyconfig.h.in b/pyconfig.h.in
index 8e8f3191e75..ca8ccb695d1 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -1,4 +1,4 @@
-/* pyconfig.h.in.  Generated from configure.in by autoheader.  */
+/* pyconfig.h.in.  Generated from configure.ac by autoheader.  */
 
 
 #ifndef Py_PYCONFIG_H