diff --git a/src/codegen/codegen_c.cc b/src/codegen/codegen_c.cc
index ad07d401ea74..786d50234ca2 100644
--- a/src/codegen/codegen_c.cc
+++ b/src/codegen/codegen_c.cc
@@ -245,9 +245,17 @@ void CodeGenC::PrintVecStore(const Variable* buffer,
   stream << ref << " = " << value << ";\n";
 }
 
+std::string CodeGenC::CastFromTo(std::string value, Type from, Type target) {
+  if (from == target) return value;
+  std::ostringstream os;
+  os << "((";
+  this->PrintType(target, os);
+  os << ")" << value << ")";
+  return os.str();
+}
+
 void CodeGenC::BindThreadIndex(const IterVar& iv) {
-  CHECK(!var_idmap_.count(iv->var.get()));
-  var_idmap_[iv->var.get()] = iv->thread_tag;
+  LOG(FATAL) << "not implemented";
 }
 
 void CodeGenC::PrintStorageSync(const Call* op) { // NOLINT(*)
diff --git a/src/codegen/codegen_c.h b/src/codegen/codegen_c.h
index 510f6ddc9070..f311ddb2c0af 100644
--- a/src/codegen/codegen_c.h
+++ b/src/codegen/codegen_c.h
@@ -150,6 +150,8 @@ class CodeGenC :
   // print reference to a buffer as type t in index.
   std::string GetBufferRef(
       Type t, const Variable* buffer, Expr index);
+  // Get a cast type from to
+  std::string CastFromTo(std::string value, Type from, Type target);
   /*!
    * \brief If buffer is allocated as type t.
    * \param buf_var The buffer variable.
diff --git a/src/codegen/codegen_cuda.cc b/src/codegen/codegen_cuda.cc
index 9847ba4661a6..5bb689df996d 100644
--- a/src/codegen/codegen_cuda.cc
+++ b/src/codegen/codegen_cuda.cc
@@ -35,6 +35,12 @@ void CodeGenCUDA::VisitStmt_(const ir::For* op) {
   CodeGenC::VisitStmt_(op);
 }
 
+void CodeGenCUDA::BindThreadIndex(const IterVar& iv) {
+  CHECK(!var_idmap_.count(iv->var.get()));
+  var_idmap_[iv->var.get()] =
+      CastFromTo(iv->thread_tag, UInt(32), iv->var.type());
+}
+
 void CodeGenCUDA::PrintType(Type t, std::ostream& os) const {  // NOLINT(*)
   int lanes = t.lanes();
   if (t.is_handle()) {
diff --git a/src/codegen/codegen_cuda.h b/src/codegen/codegen_cuda.h
index 6955b5bf77d0..7974e2c0dbb8 100644
--- a/src/codegen/codegen_cuda.h
+++ b/src/codegen/codegen_cuda.h
@@ -30,7 +30,7 @@ class CodeGenCUDA final : public CodeGenC {
       const std::string& vec, Type t, int i, std::ostream& os) final;  // NOLINT(*)
   void PrintVecElemStore(
       const std::string& vec, Type t, int i, const std::string& value) final;
-
+  void BindThreadIndex(const IterVar& iv) final;  // NOLINT(*)
   // overload visitor
   void VisitExpr_(const Broadcast* op, std::ostream& os) final; // NOLINT(*)
   void VisitStmt_(const Evaluate *op) final;
diff --git a/src/codegen/codegen_metal.cc b/src/codegen/codegen_metal.cc
index 7f8c1dd9476d..ee360c8ece50 100644
--- a/src/codegen/codegen_metal.cc
+++ b/src/codegen/codegen_metal.cc
@@ -126,6 +126,12 @@ void CodeGenMetal::AddFunction(LoweredFunc f) {
   this->stream << "}\n\n";
 }
 
+void CodeGenMetal::BindThreadIndex(const IterVar& iv) {
+  CHECK(!var_idmap_.count(iv->var.get()));
+  var_idmap_[iv->var.get()] =
+      CastFromTo(iv->thread_tag, UInt(16), iv->var.type());
+}
+
 void CodeGenMetal::PrintType(Type t, std::ostream& os) const {  // NOLINT(*)
   int lanes = t.lanes();
   if (t.is_handle()) {
diff --git a/src/codegen/codegen_metal.h b/src/codegen/codegen_metal.h
index 7331670d47c7..ebf0b9ad8319 100644
--- a/src/codegen/codegen_metal.h
+++ b/src/codegen/codegen_metal.h
@@ -24,7 +24,7 @@ class CodeGenMetal final : public CodeGenC {
   void PrintStorageScope(const std::string& scope, std::ostream& os) final; // NOLINT(*)
   void PrintStorageSync(const Call* op) final;  // NOLINT(*)
   void PrintType(Type t, std::ostream& os) const final; // NOLINT(*)
-
+  void BindThreadIndex(const IterVar& iv) final;  // NOLINT(*)
   // overload visitor
   void VisitExpr_(const Broadcast* op, std::ostream& os) final; // NOLINT(*)
 };
diff --git a/src/codegen/codegen_opencl.cc b/src/codegen/codegen_opencl.cc
index f2ad3fe55b58..dd18b3a060a0 100644
--- a/src/codegen/codegen_opencl.cc
+++ b/src/codegen/codegen_opencl.cc
@@ -35,7 +35,8 @@ void CodeGenOpenCL::BindThreadIndex(const IterVar& iv) {
   } else {
     os << "get_group_id(" << ts.dim_index << ")";
   }
-  var_idmap_[iv->var.get()] = os.str();
+  var_idmap_[iv->var.get()] =
+      CastFromTo(os.str(), UInt(64), iv->var.type());
 }
 
 void CodeGenOpenCL::PrintType(Type t, std::ostream& os) const {  // NOLINT(*)
diff --git a/src/runtime/rpc/rpc_module.cc b/src/runtime/rpc/rpc_module.cc
index af855cef060d..1b84555cc855 100644
--- a/src/runtime/rpc/rpc_module.cc
+++ b/src/runtime/rpc/rpc_module.cc
@@ -140,7 +140,7 @@ TVM_REGISTER_GLOBAL("module._RPCTimeEvaluator")
           ->GetTimeEvaluator(args[1], ctx, args[4]);
     } else {
       *rv = WrapTimeEvaluator(
-          m.GetFunction(args[1], false), ctx, args[3]);
+          m.GetFunction(args[1], false), ctx, args[4]);
     }
   });