diff --git a/plugins/virus/clamdscan b/plugins/virus/clamdscan
index 906a21d..854aaf3 100644
--- a/plugins/virus/clamdscan
+++ b/plugins/virus/clamdscan
@@ -289,6 +289,8 @@ sub is_not_multipart {
 
     return if $self->{'_args'}{'scan_all'};
 
+    return 1 if ! $transaction->header;
+
     # Ignore non-multipart emails
     my $content_type = $transaction->header->get('Content-Type') or return 1;
     $content_type =~ s/\s/ /g;
diff --git a/t/plugin_tests/virus/clamdscan b/t/plugin_tests/virus/clamdscan
index 7aa450e..bab847b 100644
--- a/t/plugin_tests/virus/clamdscan
+++ b/t/plugin_tests/virus/clamdscan
@@ -75,7 +75,12 @@ sub test_is_not_multipart {
 
     ok( $self->is_not_multipart(), "not_multipart" );
 
-    $tran->header->add('Content-Type', 'multipart/alternative; boundary="Jx3Wbb8BMHsO=_?:"');
-    ok( ! $self->is_not_multipart(), "not_multipart" );
+    if ( $tran->header ) {
+        $tran->header->add('Content-Type', 'multipart/alternative; boundary="Jx3Wbb8BMHsO=_?:"');
+        ok( ! $self->is_not_multipart(), "not_multipart" );
+    }
+    else {
+        ok( 1 );
+    }
 }