diff --git a/op25/gr-op25_repeater/lib/p25p1_fdma.cc b/op25/gr-op25_repeater/lib/p25p1_fdma.cc
index 6a8d7ea..396fb55 100644
--- a/op25/gr-op25_repeater/lib/p25p1_fdma.cc
+++ b/op25/gr-op25_repeater/lib/p25p1_fdma.cc
@@ -283,6 +283,12 @@ p25p1_fdma::process_HDU(const bit_vector& A)
 		ess_keyid = ((HB[j+2] & 0x03) << 14) + (HB[j+3] << 8) + (HB[j+4] << 2) + (HB[j+5] >> 4);	// 16 bit KeyId
 		vf_tgid   = ((HB[j+5] & 0x0f) << 12) + (HB[j+6] << 6) +  HB[j+7];				// 16 bit TGID
 
+		if (ess_algid == 0) {	// workaround spurious algid
+			ess_algid = 128;	// unenc
+			if (d_debug)
+				fprintf(stderr, "***HDU detected zero algid, msgq_id %d***\n", d_msgq_id);
+		}
+
 		if (d_debug >= 10) {
 			fprintf (stderr, "ESS: tgid=%d, mfid=%x, algid=%x, keyid=%x, mi=", vf_tgid, MFID, ess_algid, ess_keyid);
 			for (i = 0; i < 9; i++) {
@@ -374,6 +380,12 @@ p25p1_fdma::process_LDU2(const bit_vector& A)
 			ess_algid =  (HB[j  ]         <<  2) + (HB[j+1] >> 4);					// 8 bit AlgId
 			ess_keyid = ((HB[j+1] & 0x0f) << 12) + (HB[j+2] << 6) + HB[j+3];			// 16 bit KeyId
 
+			if (ess_algid == 0) {	// workaround spurious algid
+				ess_algid = 128;	// unenc
+				if (d_debug)
+					fprintf(stderr, "***LDU2 detected zero algid, msgq_id %d***\n", d_msgq_id);
+			}
+
 			if (d_debug >= 10) {
 				fprintf(stderr, "ESS: algid=%x, keyid=%x, mi=", ess_algid, ess_keyid);
 				for (int i = 0; i < 9; i++) {
diff --git a/op25/gr-op25_repeater/lib/p25p2_tdma.cc b/op25/gr-op25_repeater/lib/p25p2_tdma.cc
index 88aff51..586a0f1 100644
--- a/op25/gr-op25_repeater/lib/p25p2_tdma.cc
+++ b/op25/gr-op25_repeater/lib/p25p2_tdma.cc
@@ -206,6 +206,13 @@ void p25p2_tdma::handle_mac_ptt(const uint8_t byte_buf[], const unsigned int len
         }
         ess_algid = byte_buf[10];
         ess_keyid = (byte_buf[11] << 8) + byte_buf[12];
+
+	if (ess_algid == 0) {	// workaround spurious algid
+		ess_algid = 128;	// unenc
+		if (d_debug)
+			fprintf(stderr, "***mac_ptt detected zero algid, msgq_id %d***\n", d_msgq_id);
+	}
+
         if (d_debug >= 10) {
                 fprintf(stderr, ", algid=%x, keyid=%x, mi=", ess_algid, ess_keyid);
                 for (int i = 0; i < 9; i++) {
@@ -455,6 +462,12 @@ void p25p2_tdma::handle_4V2V_ess(const uint8_t dibits[])
                         ess_algid = (ESS_B[0] << 2) + (ESS_B[1] >> 4);
                         ess_keyid = ((ESS_B[1] & 15) << 12) + (ESS_B[2] << 6) + ESS_B[3]; 
 
+			if (ess_algid == 0) {	// workaround spurious algid
+				ess_algid = 128;	// unenc
+				if (d_debug)
+					fprintf(stderr, "***burst detected zero algid, msgq_id %d***\n", d_msgq_id);
+			}
+
                         j = 0;
                         for (i = 0; i < 9;) {
                                  ess_mi[i++] = (uint8_t)  (ESS_B[j+4]         << 2) + (ESS_B[j+5] >> 4);