diff --git a/src/mips/builtins-mips.cc b/src/mips/builtins-mips.cc
index e95c42292e..326b9e4499 100644
--- a/src/mips/builtins-mips.cc
+++ b/src/mips/builtins-mips.cc
@@ -433,9 +433,7 @@ static void Generate_JSConstructStubHelper(MacroAssembler* masm,
         __ CallRuntime(Runtime::kFinalizeInstanceSize, 1);
 
         __ Pop(a1, a2);
-        // Slack tracking counter is Map::kSlackTrackingCounterEnd after runtime
-        // call.
-        __ li(t2, Map::kSlackTrackingCounterEnd);
+        __ li(t2, Operand(Map::kSlackTrackingCounterEnd - 1));
 
         __ bind(&allocate);
       }
diff --git a/src/mips64/builtins-mips64.cc b/src/mips64/builtins-mips64.cc
index 30a93dc5eb..e97cca21d1 100644
--- a/src/mips64/builtins-mips64.cc
+++ b/src/mips64/builtins-mips64.cc
@@ -434,9 +434,7 @@ static void Generate_JSConstructStubHelper(MacroAssembler* masm,
         __ CallRuntime(Runtime::kFinalizeInstanceSize, 1);
 
         __ Pop(a1, a2);
-        // Slack tracking counter is Map::kSlackTrackingCounterEnd after runtime
-        // call.
-        __ li(a6, Map::kSlackTrackingCounterEnd);
+        __ li(a6, Operand(Map::kSlackTrackingCounterEnd - 1));
 
         __ bind(&allocate);
       }