diff --git a/target/mips/cpu.h b/target/mips/cpu.h
index 4cbc31c3e8d2..0086f95ea2a3 100644
--- a/target/mips/cpu.h
+++ b/target/mips/cpu.h
@@ -828,7 +828,7 @@ struct CPUMIPSState {
 #define CP0EBase_WG 11
     target_ulong CP0_CMGCRBase;
 /*
- * CP0 Register 16
+ * CP0 Register 16 (after Release 1)
  */
     int32_t CP0_Config0;
 #define CP0C0_M    31
@@ -845,6 +845,14 @@ struct CPUMIPSState {
 #define CP0C0_VI   3
 #define CP0C0_K0   0     /*  2..0  */
 #define CP0C0_AR_LENGTH 3
+/*
+ * CP0 Register 16 (before Release 1)
+ */
+#define CP0C0_Impl 16    /* 24..16 */
+#define CP0C0_IC   9     /* 11..9 */
+#define CP0C0_DC   6     /*  8..6 */
+#define CP0C0_IB   5
+#define CP0C0_DB   4
     int32_t CP0_Config1;
 #define CP0C1_M    31
 #define CP0C1_MMU  25    /* 30..25 */