diff --git a/source/core/Pipeline.cpp b/source/core/Pipeline.cpp
index 8c83307f..fad7680d 100644
--- a/source/core/Pipeline.cpp
+++ b/source/core/Pipeline.cpp
@@ -87,7 +87,6 @@ Pipeline::Unit::Unit(const Op* op, const std::vector<Tensor*>& inputs, const std
     if (nullptr != typeStr) {
         mContent->type = typeStr;
     }
-    mComputer = SizeComputerSuite::get()->search(mType);
 }
 
 
@@ -178,6 +177,11 @@ ErrorCode Pipeline::Unit::prepare(Backend* bn, Backend* cpuBn) {
         if (o->size() <= 0) {
             ready = false;
         }
+        if (o->dimensions() < 4 && TensorUtils::getDescribe(o)->dimensionFormat == MNN_DATA_FORMAT_NC4HW4) {
+            for (auto index = o->dimensions(); index < 4; ++index) {
+                o->setLength(index, 1);
+            }
+        }
     }
     mContent->flops = SizeComputer::computeFlops(mOriginOp, mInputs, mOutputs);
 
diff --git a/source/core/Pipeline.hpp b/source/core/Pipeline.hpp
index 10c8718b..f36d8a6b 100644
--- a/source/core/Pipeline.hpp
+++ b/source/core/Pipeline.hpp
@@ -102,7 +102,6 @@ public:
 
     private:
         bool mConst                   = false;
-        const SizeComputer* mComputer = nullptr;
     };
 
 protected: