diff --git a/frontends/ast/ast.cc b/frontends/ast/ast.cc
index 5f95de35f..49b256d02 100644
--- a/frontends/ast/ast.cc
+++ b/frontends/ast/ast.cc
@@ -223,6 +223,7 @@ AstNode::AstNode(AstNodeType type, AstNode *child1, AstNode *child2, AstNode *ch
 	was_checked = false;
 	range_valid = false;
 	range_swapped = false;
+	is_sbvector = false;
 	is_custom_type = false;
 	port_id = 0;
 	range_left = -1;