diff --git a/apache2/msc_multipart.c b/apache2/msc_multipart.c
index d96fc8132..5a981cfba 100644
--- a/apache2/msc_multipart.c
+++ b/apache2/msc_multipart.c
@@ -149,6 +149,7 @@ static int multipart_parse_content_disposition(modsec_rec *msr, char *c_d_value)
                 p++;
             }
             if (*p != '\'') {
+                msr->mpd->flag_invalid_quoting = 1;
                 return -17; // Single quote for end-of-language not found
             }
             p++;