diff --git a/mace/kernels/activation.h b/mace/kernels/activation.h
index b768eb28c93a52502af8dd51f0e6aa13a9a145a8..c9f8dac5873a3cedcac4ff4cddd92c89b91ef9a3 100644
--- a/mace/kernels/activation.h
+++ b/mace/kernels/activation.h
@@ -116,7 +116,8 @@ class ActivationFunctor {
     const T *input_ptr = input->data<T>();
     T *output_ptr = output->mutable_data<T>();
     if (activation_ == PRELU) {
-      const T *alpha_ptr = alpha == nullptr ? nullptr : alpha->data<T>();
+      MACE_CHECK(alpha != nullptr) << "PReLU's alpha parameter shouldn't be null";
+      const T *alpha_ptr = alpha->data<T>();
       PReLUActivation(input_ptr, output->size(), input->dim(3), alpha_ptr, output_ptr); 
     } else {
       DoActivation(input_ptr, output_ptr, output->size(), activation_, relux_max_limit_);
diff --git a/mace/ops/activation_benchmark.cc b/mace/ops/activation_benchmark.cc
index 1037bdcb453e2dc46c0750815c61e1c2fc836ddc..4e904fce84e31762dc03fe23f3047d21d1293eca 100644
--- a/mace/ops/activation_benchmark.cc
+++ b/mace/ops/activation_benchmark.cc
@@ -139,23 +139,26 @@ static void PreluBenchmark(
 
   // Add input data
   net.AddRandomInput<D, float>("Input", {batch, height, width, channels});
+  net.AddRandomInput<D, float>("Alpha", {channels});
 
   if (D == DeviceType::OPENCL) {
     BufferToImage<D, float>(net, "Input", "InputImage",
                             kernels::BufferType::IN_OUT_CHANNEL);
+    BufferToImage<D, float>(net, "Alpha", "AlphaImage",
+                            kernels::BufferType::ARGUMENT);
 
     OpDefBuilder("Activation", "PreluBM")
         .Input("InputImage")
+        .Input("AlphaImage")
         .Output("Output")
         .AddStringArg("activation", "PRELU")
-        .AddFloatArg("alpha", 2.0)
         .Finalize(net.NewOperatorDef());
   } else {
     OpDefBuilder("Activation", "PreluBM")
         .Input("Input")
+        .Input("Alpha")
         .Output("Output")
         .AddStringArg("activation", "PRELU")
-        .AddFloatArg("alpha", 2.0)
         .Finalize(net.NewOperatorDef());
   }