diff --git a/configure.ac b/configure.ac
index 02d79665cc115011d1e269c973e043772fff0d9c..ff4a978e591b711318fb3f6ae08f7edf20181301 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2,7 +2,7 @@ AC_PREREQ([2.59])
 
 # Be sure to update ABI version also if anything changes that might require
 # recompiling plugins. Most importantly that means if any structs are changed.
-AC_INIT([Pigeonhole], [0.4.devel], [dovecot@dovecot.org], [dovecot-2.2-pigeonhole])
+AC_INIT([Pigeonhole], [0.5.devel], [dovecot@dovecot.org], [dovecot-2.2-pigeonhole])
 AC_DEFINE_UNQUOTED([PIGEONHOLE_ABI_VERSION], "0.4.ABIv2($PACKAGE_VERSION)", [Pigeonhole ABI version])
 
 AC_CONFIG_AUX_DIR([.])