diff --git a/src/pattern.c b/src/pattern.c
index a6fc52d61..b19ffe273 100644
--- a/src/pattern.c
+++ b/src/pattern.c
@@ -1308,6 +1308,10 @@ void pat_del_tree_str(struct pattern_expr *expr, struct pat_ref_elt *ref)
 	struct ebmb_node *node, *next_node;
 	struct pattern_tree *elt;
 
+	/* If the flag PAT_F_IGNORE_CASE is set, we cannot use trees */
+	if (expr->mflags & PAT_MF_IGNORE_CASE)
+		return pat_del_list_ptr(expr, ref);
+
 	/* browse each node of the tree. */
 	for (node = ebmb_first(&expr->pattern_tree), next_node = node ? ebmb_next(node) : NULL;
 	     node;