diff --git a/configure.ac b/configure.ac
index 7dcbdde65d..0e8922da40 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4,7 +4,7 @@ dnl Copyright (c) 2007-2019, The Tor Project, Inc.
 dnl See LICENSE for licensing information
 
 AC_PREREQ([2.63])
-AC_INIT([tor],[0.4.6.6])
+AC_INIT([tor],[0.4.6.6-dev])
 AC_CONFIG_SRCDIR([src/app/main/tor_main.c])
 AC_CONFIG_MACRO_DIR([m4])
 
@@ -18,7 +18,7 @@ AC_DEFINE_UNQUOTED([CONFIG_FLAGS], ["$configure_flags"], [Flags passed to config
 # version number changes.  Tor uses it to make sure that it
 # only shuts down for missing "required protocols" when those protocols
 # are listed as required by a consensus after this date.
-AC_DEFINE(APPROX_RELEASE_DATE, ["2021-06-30"], # for 0.4.6.6
+AC_DEFINE(APPROX_RELEASE_DATE, ["2021-06-30"], # for 0.4.6.6-dev
           [Approximate date when this software was released. (Updated when the version changes.)])
 
 # "foreign" means we don't follow GNU package layout standards
diff --git a/contrib/win32build/tor-mingw.nsi.in b/contrib/win32build/tor-mingw.nsi.in
index 9728648d28..71456db258 100644
--- a/contrib/win32build/tor-mingw.nsi.in
+++ b/contrib/win32build/tor-mingw.nsi.in
@@ -8,7 +8,7 @@
 !include "LogicLib.nsh"
 !include "FileFunc.nsh"
 !insertmacro GetParameters
-!define VERSION "0.4.6.6"
+!define VERSION "0.4.6.6-dev"
 !define INSTALLER "tor-${VERSION}-win32.exe"
 !define WEBSITE "https://www.torproject.org/"
 !define LICENSE "LICENSE"
diff --git a/src/win32/orconfig.h b/src/win32/orconfig.h
index f18b7a5fd8..c745d16568 100644
--- a/src/win32/orconfig.h
+++ b/src/win32/orconfig.h
@@ -217,7 +217,7 @@
 #define USING_TWOS_COMPLEMENT
 
 /* Version number of package */
-#define VERSION "0.4.6.6"
+#define VERSION "0.4.6.6-dev"
 
 #define HAVE_STRUCT_SOCKADDR_IN6
 #define HAVE_STRUCT_IN6_ADDR