diff --git a/target-mips/helper.c b/target-mips/helper.c
index c23e9c6b37..71a9723396 100644
--- a/target-mips/helper.c
+++ b/target-mips/helper.c
@@ -403,7 +403,7 @@ void do_interrupt (CPUState *env)
             env->PC = (int32_t)(env->CP0_EBase & ~0x3ff);
         }
         env->PC += offset;
-        env->CP0_Cause = (env->CP0_Cause & ~0x7C) | (cause << 2);
+        env->CP0_Cause = (env->CP0_Cause & ~(0x1f << CP0Ca_EC)) | (cause << CP0Ca_EC);
         break;
     default:
         if (logfile) {
diff --git a/target-mips/op.c b/target-mips/op.c
index 9818847fe3..3951204169 100644
--- a/target-mips/op.c
+++ b/target-mips/op.c
@@ -1401,7 +1401,7 @@ void op_mtc0_cause (void)
     if ((env->CP0_Config0 & (0x7 << CP0C0_AR)) == (1 << CP0C0_AR))
         mask |= 1 << CP0Ca_DC;
 
-    env->CP0_Cause = (env->CP0_Cause & 0xFCC0FF7C) | (T0 & mask);
+    env->CP0_Cause = (env->CP0_Cause & ~mask) | (T0 & mask);
 
     /* Handle the software interrupt as an hardware one, as they
        are very similar */