diff --git a/lib/ts_bm.c b/lib/ts_bm.c
index d90822c..4a7fce7 100644
--- a/lib/ts_bm.c
+++ b/lib/ts_bm.c
@@ -63,7 +63,7 @@
 	struct ts_bm *bm = ts_config_priv(conf);
 	unsigned int i, text_len, consumed = state->offset;
 	const u8 *text;
-	int shift = bm->patlen, bs;
+	int shift = bm->patlen - 1, bs;
 
 	for (;;) {
 		text_len = conf->get_next_block(consumed, &text, conf, state);