diff --git a/include/osmocom/gsm/protocol/gsm_04_08.h b/include/osmocom/gsm/protocol/gsm_04_08.h
index 68ec4e3..8370eca 100644
--- a/include/osmocom/gsm/protocol/gsm_04_08.h
+++ b/include/osmocom/gsm/protocol/gsm_04_08.h
@@ -889,13 +889,25 @@
 #if OSMO_IS_LITTLE_ENDIAN
 	uint8_t spare:4,
 		 key_seq:4;
-	uint32_t classmark2;
+	union {
+		uint32_t classmark2;  /* Backward compatibility */
+		struct {
+			uint8_t cm2_len;
+			struct gsm48_classmark2 cm2;
+		};
+	};
 	uint8_t mi_len;
 	uint8_t mi[0];
 #elif OSMO_IS_BIG_ENDIAN
 /* auto-generated from the little endian part above (libosmocore/contrib/struct_endianess.py) */
 	uint8_t key_seq:4, spare:4;
-	uint32_t classmark2;
+	union {
+		uint32_t classmark2;  /* Backward compatibility */
+		struct {
+			uint8_t cm2_len;
+			struct gsm48_classmark2 cm2;
+		};
+	};
 	uint8_t mi_len;
 	uint8_t mi[0];
 #endif
@@ -1027,15 +1039,26 @@
 #if OSMO_IS_LITTLE_ENDIAN
 	uint8_t cm_service_type : 4,
 		 cipher_key_seq  : 4;
-	/* length + 3 bytes */
-	uint32_t classmark;
+	union {
+		uint32_t classmark;  /* Backward compatibility */
+		struct {
+			uint8_t cm2_len;
+			struct gsm48_classmark2 classmark2;
+		};
+	};
 	uint8_t mi_len;
 	uint8_t mi[0];
 	/* optional priority level */
 #elif OSMO_IS_BIG_ENDIAN
 /* auto-generated from the little endian part above (libosmocore/contrib/struct_endianess.py) */
 	uint8_t cipher_key_seq:4, cm_service_type:4;
-	uint32_t classmark;
+	union {
+		uint32_t classmark;  /* Backward compatibility */
+		struct {
+			uint8_t cm2_len;
+			struct gsm48_classmark2 classmark2;
+		};
+	};
 	uint8_t mi_len;
 	uint8_t mi[0];
 #endif