diff --git a/src/lib-sieve/plugins/mailbox/Makefile.am b/src/lib-sieve/plugins/mailbox/Makefile.am
index 7e93fa984f9c0bce565e8674a6d93c967a4158e4..cb5ec82191e799db1e274ebaed6eb2ed7fdc4eae 100644
--- a/src/lib-sieve/plugins/mailbox/Makefile.am
+++ b/src/lib-sieve/plugins/mailbox/Makefile.am
@@ -14,7 +14,6 @@ commands = \
 	cmd-mailboxexists.c
 
 libsieve_ext_mailbox_la_SOURCES = \
-	ext-mailbox-commonc \
 	$(tags) \
 	$(commands) \
 	ext-mailbox.c