diff --git a/target/mips/cpu.c b/target/mips/cpu.c
index ad74fbe636..c15c955367 100644
--- a/target/mips/cpu.c
+++ b/target/mips/cpu.c
@@ -305,7 +305,7 @@ static void mips_cpu_reset(DeviceState *dev)
 
         for (i = 0; i < 7; i++) {
             env->CP0_WatchLo[i] = 0;
-            env->CP0_WatchHi[i] = 0x80000000;
+            env->CP0_WatchHi[i] = 1 << CP0WH_M;
         }
         env->CP0_WatchLo[7] = 0;
         env->CP0_WatchHi[7] = 0;
diff --git a/target/mips/cpu.h b/target/mips/cpu.h
index 5335ac10a3..6b6b8776d1 100644
--- a/target/mips/cpu.h
+++ b/target/mips/cpu.h
@@ -1005,6 +1005,7 @@ typedef struct CPUArchState {
  */
     uint64_t CP0_WatchHi[8];
 #define CP0WH_ASID 16
+#define CP0WH_M    31
 /*
  * CP0 Register 20
  */
diff --git a/target/mips/tcg/sysemu/cp0_helper.c b/target/mips/tcg/sysemu/cp0_helper.c
index aae2af6ecc..5da1124589 100644
--- a/target/mips/tcg/sysemu/cp0_helper.c
+++ b/target/mips/tcg/sysemu/cp0_helper.c
@@ -1396,10 +1396,11 @@ void helper_mtc0_watchlo(CPUMIPSState *env, target_ulong arg1, uint32_t sel)
 void helper_mtc0_watchhi(CPUMIPSState *env, target_ulong arg1, uint32_t sel)
 {
     uint64_t mask = 0x40000FF8 | (env->CP0_EntryHi_ASID_mask << CP0WH_ASID);
+    uint64_t m_bit = env->CP0_WatchHi[sel] & (1 << CP0WH_M); /* read-only */
     if ((env->CP0_Config5 >> CP0C5_MI) & 1) {
         mask |= 0xFFFFFFFF00000000ULL; /* MMID */
     }
-    env->CP0_WatchHi[sel] = arg1 & mask;
+    env->CP0_WatchHi[sel] = m_bit | (arg1 & mask);
     env->CP0_WatchHi[sel] &= ~(env->CP0_WatchHi[sel] & arg1 & 0x7);
 }