diff --git a/checks.c b/checks.c
index 45d0213..946c142 100644
--- a/checks.c
+++ b/checks.c
@@ -324,7 +324,7 @@ ERROR(node_name_chars, check_node_name_chars, NODECHARS);
 static void check_node_name_chars_strict(struct check *c, struct dt_info *dti,
 					 struct node *node)
 {
-	int n = strspn(node->name, c->data);
+	size_t n = strspn(node->name, c->data);
 
 	if (n < node->basenamelen)
 		FAIL(c, dti, node, "Character '%c' not recommended in node name",
diff --git a/dtc.h b/dtc.h
index 7231200..473552e 100644
--- a/dtc.h
+++ b/dtc.h
@@ -227,7 +227,7 @@ struct node {
 	struct node *next_sibling;
 
 	char *fullpath;
-	int basenamelen;
+	size_t basenamelen;
 
 	cell_t phandle;
 	int addr_cells, size_cells;