diff --git a/js/src/jit/IonBuilder.cpp b/js/src/jit/IonBuilder.cpp
index 7dc2de55c1b9..700e68670016 100644
--- a/js/src/jit/IonBuilder.cpp
+++ b/js/src/jit/IonBuilder.cpp
@@ -12110,7 +12110,7 @@ AbortReasonOr<Ok> IonBuilder::jsop_globalthis() {
 
 AbortReasonOr<Ok> IonBuilder::jsop_typeof() {
   MDefinition* input = current->pop();
-  MTypeOf* ins = MTypeOf::New(alloc(), input, input->type());
+  MTypeOf* ins = MTypeOf::New(alloc(), input);
 
   ins->cacheInputMaybeCallableOrEmulatesUndefined(constraints());
 
diff --git a/js/src/jit/MIR.cpp b/js/src/jit/MIR.cpp
index 3729f300aea7..754817030443 100644
--- a/js/src/jit/MIR.cpp
+++ b/js/src/jit/MIR.cpp
@@ -3540,13 +3540,13 @@ MDefinition* MBitNot::foldsTo(TempAllocator& alloc) {
 }
 
 MDefinition* MTypeOf::foldsTo(TempAllocator& alloc) {
-  // Note: we can't use input->type() here, type analysis has
-  // boxed the input.
-  MOZ_ASSERT(input()->type() == MIRType::Value);
+  if (!input()->isBox()) {
+    return this;
+  }
 
+  MDefinition* unboxed = input()->toBox()->input();
   JSType type;
-
-  switch (inputType()) {
+  switch (unboxed->type()) {
     case MIRType::Double:
     case MIRType::Float32:
     case MIRType::Int32:
diff --git a/js/src/jit/MIR.h b/js/src/jit/MIR.h
index 8b8d1d058492..21c592e63a6a 100644
--- a/js/src/jit/MIR.h
+++ b/js/src/jit/MIR.h
@@ -4482,12 +4482,10 @@ class MBitNot : public MUnaryInstruction, public BitwisePolicy::Data {
 };
 
 class MTypeOf : public MUnaryInstruction, public BoxInputsPolicy::Data {
-  MIRType inputType_;
   bool inputMaybeCallableOrEmulatesUndefined_;
 
-  MTypeOf(MDefinition* def, MIRType inputType)
+  explicit MTypeOf(MDefinition* def)
       : MUnaryInstruction(classOpcode, def),
-        inputType_(inputType),
         inputMaybeCallableOrEmulatesUndefined_(true) {
     setResultType(MIRType::String);
     setMovable();
@@ -4497,8 +4495,6 @@ class MTypeOf : public MUnaryInstruction, public BoxInputsPolicy::Data {
   INSTRUCTION_HEADER(TypeOf)
   TRIVIAL_NEW_WRAPPERS
 
-  MIRType inputType() const { return inputType_; }
-
   MDefinition* foldsTo(TempAllocator& alloc) override;
   void cacheInputMaybeCallableOrEmulatesUndefined(
       CompilerConstraintList* constraints);
@@ -4516,9 +4512,6 @@ class MTypeOf : public MUnaryInstruction, public BoxInputsPolicy::Data {
     if (!ins->isTypeOf()) {
       return false;
     }
-    if (inputType() != ins->toTypeOf()->inputType()) {
-      return false;
-    }
     if (inputMaybeCallableOrEmulatesUndefined() !=
         ins->toTypeOf()->inputMaybeCallableOrEmulatesUndefined()) {
       return false;
diff --git a/js/src/jit/WarpBuilder.cpp b/js/src/jit/WarpBuilder.cpp
index efefbbef1dd6..853ca281f284 100644
--- a/js/src/jit/WarpBuilder.cpp
+++ b/js/src/jit/WarpBuilder.cpp
@@ -1525,9 +1525,8 @@ bool WarpBuilder::build_ToPropertyKey(BytecodeLocation loc) {
 }
 
 bool WarpBuilder::build_Typeof(BytecodeLocation) {
-  // TODO: remove MTypeOf::inputType_ and unbox in foldsTo instead.
   MDefinition* input = current->pop();
-  MTypeOf* ins = MTypeOf::New(alloc(), input, MIRType::Value);
+  MTypeOf* ins = MTypeOf::New(alloc(), input);
   current->add(ins);
   current->push(ins);
   return true;