diff --git a/storage/innobase/row/row0sel.c b/storage/innobase/row/row0sel.c
index e4c7e37307b..518eba975ab 100644
--- a/storage/innobase/row/row0sel.c
+++ b/storage/innobase/row/row0sel.c
@@ -217,7 +217,8 @@ row_sel_sec_rec_is_for_clust_rec(
 
 		len = clust_len;
 
-		if (ifield->prefix_len > 0 && len != UNIV_SQL_NULL) {
+		if (ifield->prefix_len > 0 && len != UNIV_SQL_NULL
+		    && sec_len != UNIV_SQL_NULL) {
 
 			if (rec_offs_nth_extern(clust_offs, clust_pos)) {
 				len -= BTR_EXTERN_FIELD_REF_SIZE;