diff --git a/src/operator/optimizer_op-inl.h b/src/operator/optimizer_op-inl.h
index 698f7977a963..e28c061122bc 100644
--- a/src/operator/optimizer_op-inl.h
+++ b/src/operator/optimizer_op-inl.h
@@ -1567,7 +1567,7 @@ struct LambUpdatePhaseOneParam : public dmlc::Parameter<LambUpdatePhaseOneParam>
     float beta1;
     float beta2;
     float epsilon;
-    float t;
+    int t;
     bool bias_correction;
     float wd;
     float rescale_grad;
@@ -1624,7 +1624,7 @@ struct LambUpdatePhaseOneKernel {
     DType* mean_data, DType* var_data, const DType* weight_data, const DType* grad_data,
     const DType clip_gradient, const DType rescale_grad,
     const DType beta1, const DType beta2, const DType wd,
-    const DType epsilon, const DType t,
+    const DType epsilon, const int t,
     bool bias_correction, const OpReqType req) {
     using namespace mshadow_op;
 
@@ -1639,8 +1639,8 @@ struct LambUpdatePhaseOneKernel {
     DType g = mean_data[i] / (square_root::Map(var_data[i]) + epsilon) + wd * weight_data[i];
 
     if (bias_correction) {
-      DType mean_hat = mean_data[i] / (1. - power::Map(beta1, t));
-      DType var_hat = var_data[i] / (1 - power::Map(beta2, t));
+      DType mean_hat = mean_data[i] / (1. - std::pow(beta1, t));
+      DType var_hat = var_data[i] / (1 - std::pow(beta2, t));
       g = mean_hat / (square_root::Map(var_hat) + epsilon) + wd * weight_data[i];
     }
     KERNEL_ASSIGN(out_data[i], req, g);
@@ -1668,7 +1668,7 @@ inline void LambUpdatePhaseOne(const nnvm::NodeAttrs& attrs,
     static_cast<DType>(param.clip_gradient), static_cast<DType>(param.rescale_grad),
     static_cast<DType>(param.beta1), static_cast<DType>(param.beta2),
     static_cast<DType>(param.wd), static_cast<DType>(param.epsilon),
-    static_cast<DType>(param.t), static_cast<bool>(param.bias_correction), req[0]);
+    static_cast<int>(param.t), static_cast<bool>(param.bias_correction), req[0]);
   });
 }