diff --git a/src/target/firmware/layer1/l23_api.c b/src/target/firmware/layer1/l23_api.c
index daffaf8b6..e78020def 100644
--- a/src/target/firmware/layer1/l23_api.c
+++ b/src/target/firmware/layer1/l23_api.c
@@ -97,10 +97,13 @@ static uint32_t chan_nr2mf_task_mask(uint8_t chan_nr, uint8_t neigh_mode)
 		lch_idx = cbits & 0x7;
 		master_task = MF_TASK_SDCCH8_0 + lch_idx;
 		multiframe = MF51;
-	} else if ((cbits & 0x1e) == 0x18) {
-		/* Osmocom specific extension for CBCH */
-		master_task = (cbits & 0x01) ? /* 0b1100T */
-			MF_TASK_SDCCH4_CBCH : MF_TASK_SDCCH8_CBCH;
+	} else if ((cbits & 0x1f) == 0x19) {
+		/* Osmocom specific extension for CBCH on SDCCH/4 */
+		master_task = MF_TASK_SDCCH4_CBCH;
+		multiframe = MF51;
+	} else if ((cbits & 0x1f) == 0x1a) {
+		/* Osmocom specific extension for CBCH on SDCCH/8 */
+		master_task = MF_TASK_SDCCH8_CBCH;
 		multiframe = MF51;
 #if 0
 	} else if (cbits == 0x10) {
@@ -141,10 +144,12 @@ static int  chan_nr2dchan_type(uint8_t chan_nr)
 		return GSM_DCHAN_SDCCH_4;
 	} else if ((cbits & 0x18) == 0x08) {
 		return GSM_DCHAN_SDCCH_8;
-	} else if ((cbits & 0x1e) == 0x18) {
-		/* Osmocom-specific extension for CBCH */
-		return (cbits & 0x01) ? /* 0b1100T */
-			GSM_DCHAN_SDCCH_8_CBCH : GSM_DCHAN_SDCCH_4_CBCH;
+	} else if ((cbits & 0x1f) == 0x19) {
+		/* Osmocom-specific extension for CBCH on SDCCH/4 */
+		return GSM_DCHAN_SDCCH_4_CBCH;
+	} else if ((cbits & 0x1f) == 0x1a) {
+		/* Osmocom-specific extension for CBCH on SDCCH/8 */
+		return GSM_DCHAN_SDCCH_8_CBCH;
 	}
 
 	return GSM_DCHAN_UNKNOWN;
diff --git a/src/target/firmware/layer1/mframe_sched.c b/src/target/firmware/layer1/mframe_sched.c
index 7fa38c138..9c2954c3f 100644
--- a/src/target/firmware/layer1/mframe_sched.c
+++ b/src/target/firmware/layer1/mframe_sched.c
@@ -416,10 +416,10 @@ uint8_t mframe_task2chan_nr(enum mframe_task mft, uint8_t ts)
 
 	/* Osmocom specific extensions */
 	case MF_TASK_SDCCH4_CBCH:
-		cbits = 0x18;
+		cbits = 0x19;
 		break;
 	case MF_TASK_SDCCH8_CBCH:
-		cbits = 0x19;
+		cbits = 0x1a;
 		break;
 
 	case MF_TASK_UL_ALL_NB: