diff --git a/dumb/src/it/itread.c b/dumb/src/it/itread.c
index e8661807e..ca1dde55d 100644
--- a/dumb/src/it/itread.c
+++ b/dumb/src/it/itread.c
@@ -290,12 +290,15 @@ static int it_read_envelope(IT_ENVELOPE *envelope, DUMBFILE *f)
 
 	envelope->flags = dumbfile_getc(f);
 	envelope->n_nodes = dumbfile_getc(f);
+	if(envelope->n_nodes > 25) {
+		TRACE("IT error: wrong number of envelope nodes (%d)\n", envelope->n_nodes);
+		envelope->n_nodes = 0;
+		return -1;
+	}
 	envelope->loop_start = dumbfile_getc(f);
 	envelope->loop_end = dumbfile_getc(f);
 	envelope->sus_loop_start = dumbfile_getc(f);
 	envelope->sus_loop_end = dumbfile_getc(f);
-	if (envelope->n_nodes > 25)
-		envelope->n_nodes = 25;
 	for (n = 0; n < envelope->n_nodes; n++) {
 		envelope->node_y[n] = dumbfile_getc(f);
 		envelope->node_t[n] = dumbfile_igetw(f);