diff --git a/dnn/src/common/cv/filter.cpp b/dnn/src/common/cv/filter.cpp
index c40a0ca35cc22c8c89407b4262d10dd75de0a42e..8749752d879689259af025d6c91d302d695ea757 100644
--- a/dnn/src/common/cv/filter.cpp
+++ b/dnn/src/common/cv/filter.cpp
@@ -85,9 +85,7 @@ FilterEngine<ST, FT>::FilterEngine(
     m_buf_step = 0;
 
     //! the anchor must be in the kernerl
-    megdnn_assert(
-            0 <= m_anchor.x && m_anchor.x < m_ksize.cols() && 0 <= m_anchor.y &&
-            m_anchor.y < m_ksize.rows());
+    megdnn_assert(m_anchor.x < m_ksize.cols() && m_anchor.y < m_ksize.rows());
 
     int src_elem_size = (int)sizeof(ST) * m_ch;
     m_border_elem_size = src_elem_size / ((sizeof(ST) >= 4) ? sizeof(int) : 1);
diff --git a/src/core/impl/tensor.cpp b/src/core/impl/tensor.cpp
index d5ba18824e68ca13687546553d527f204db6bd71..ee01694073a0301dda3c4cca6c5558f1bf66e110 100644
--- a/src/core/impl/tensor.cpp
+++ b/src/core/impl/tensor.cpp
@@ -494,7 +494,7 @@ DEF(reset, &)(TensorStorage storage, const TensorLayout& layout) {
     if (span.last_elem == span.high_elem) {
         mgb_assert(!layout.ndim || storage.valid_span(span) || storage.empty());
     } else {
-        size_t start_pos = span.low_byte + static_cast<ptrdiff_t>(storage.offset());
+        int64_t start_pos = span.low_byte + static_cast<ptrdiff_t>(storage.offset());
         bool enough_size = span.last_byte <= storage.size();
         bool valid_size = storage.comp_node().valid() && start_pos >= 0 && enough_size;
         mgb_assert(!layout.ndim || valid_size || storage.empty());