diff --git a/src/lib-sieve/plugins/imap4flags/tag-flags.c b/src/lib-sieve/plugins/imap4flags/tag-flags.c
index d8fc8c23071ae4b1d98ff93167ac44e9d4da2ffb..d794875998236af42aee4ed71db1d6238f6de8d7 100644
--- a/src/lib-sieve/plugins/imap4flags/tag-flags.c
+++ b/src/lib-sieve/plugins/imap4flags/tag-flags.c
@@ -340,7 +340,8 @@ static int seff_flags_merge
 	const struct sieve_side_effect *new_seffect, 	
 	void **old_context)
 {
-	*old_context = new_seffect->context;
+	if ( new_seffect != NULL )
+		*old_context = new_seffect->context;
 	
 	return 1;
 }