diff --git a/plugins/greylisting b/plugins/greylisting
index 12926a2..72b04f2 100644
--- a/plugins/greylisting
+++ b/plugins/greylisting
@@ -502,7 +502,7 @@ sub prune_db {
 
     my @to_delete;
     my $greylist = {};
-    my @keys = $self->db->get_keys or return;
+    my @keys = $self->db->get_keys or return $self->db->unlock;
     @$greylist{ @keys } = ( $self->db->mget(@keys) );
     for my $key ( @keys ) {
         my ($ts) = split /:/, delete $greylist->{$key};
@@ -510,7 +510,7 @@ sub prune_db {
         next if $age < $self->{_args}{white_timeout};
         push @to_delete, $key;
     }
-    return if ! @to_delete;
+    return $self->db->unlock if ! @to_delete;
     my $pruned = $self->db->delete(@to_delete);
     $self->db->unlock;
     $self->log(LOGINFO, "pruned $pruned of $count DB entries");
diff --git a/t/plugin_tests/greylisting b/t/plugin_tests/greylisting
index d4b32b5..dc5a6d6 100644
--- a/t/plugin_tests/greylisting
+++ b/t/plugin_tests/greylisting
@@ -264,6 +264,12 @@ sub test_prune_db {
         is( $self->allkeys, '',
             'prune_db() expires all remaining keys 37 days later' );
     }
+    # Ensure prune_db does not leave the database locked after doing nothing
+    delete $self->{db};
+    $self->db( class => 'Qpsmtpd::DB::File::DBM', dir => 't/tmp' );
+    $self->prune_db;
+    $self->prune_db;
+    ok(1, "We won't get this far if prune_db leaves the database locked");
 }
 
 sub allkeys {