diff --git a/software/obsolete/osmo_e1f.c b/software/obsolete/osmo_e1f.c
index a4cadb2..2c3fcfb 100644
--- a/software/obsolete/osmo_e1f.c
+++ b/software/obsolete/osmo_e1f.c
@@ -233,7 +233,7 @@
 		case 13:
 		case 15:
 			ret = 0x40;
-			if (e1i->tx.crc4_error)
+			if (!e1i->tx.crc4_error)
 				ret |= 0x80;
 			break;
 		}