diff --git a/libs/full/parcelport_lci/include/hpx/parcelport_lci/header.hpp b/libs/full/parcelport_lci/include/hpx/parcelport_lci/header.hpp
index 5d871462b3dd..aa0a718ac600 100644
--- a/libs/full/parcelport_lci/include/hpx/parcelport_lci/header.hpp
+++ b/libs/full/parcelport_lci/include/hpx/parcelport_lci/header.hpp
@@ -69,11 +69,10 @@ namespace hpx::parcelset::policies::lci {
             {
                 HPX_ASSERT(buffer.transmission_chunks_.size() ==
                     size_t(num_zero_copy_chunks + num_non_zero_copy_chunks));
-                int tchunk_size =
-                    static_cast<int>(buffer.transmission_chunks_.size() *
-                        sizeof(typename parcel_buffer<buffer_type,
-                            ChunkType>::transmission_chunk_type));
-                if (tchunk_size <= int(max_header_size - current_header_size))
+                size_t tchunk_size = buffer.transmission_chunks_.size() *
+                    sizeof(typename parcel_buffer<buffer_type,
+                        ChunkType>::transmission_chunk_type);
+                if (tchunk_size <= max_header_size - current_header_size)
                 {
                     current_header_size += tchunk_size;
                 }
@@ -118,12 +117,11 @@ namespace hpx::parcelset::policies::lci {
             {
                 HPX_ASSERT(buffer.transmission_chunks_.size() ==
                     size_t(num_zero_copy_chunks + num_non_zero_copy_chunks));
-                int tchunk_size =
-                    static_cast<int>(buffer.transmission_chunks_.size() *
-                        sizeof(typename parcel_buffer<buffer_type,
-                            ChunkType>::transmission_chunk_type));
+                size_t tchunk_size = buffer.transmission_chunks_.size() *
+                    sizeof(typename parcel_buffer<buffer_type,
+                        ChunkType>::transmission_chunk_type);
                 set<pos_numbytes_tchunk>(static_cast<value_type>(tchunk_size));
-                if (tchunk_size <= int(max_header_size - current_header_size))
+                if (tchunk_size <= max_header_size - current_header_size)
                 {
                     data_[pos_piggy_back_flag_tchunk] = 1;
                     std::memcpy(&data_[current_header_size],
diff --git a/libs/full/parcelport_lci/include/hpx/parcelport_lci/putva/receiver_putva.hpp b/libs/full/parcelport_lci/include/hpx/parcelport_lci/putva/receiver_putva.hpp
index 2419ff28257e..cdfdd1d01f82 100644
--- a/libs/full/parcelport_lci/include/hpx/parcelport_lci/putva/receiver_putva.hpp
+++ b/libs/full/parcelport_lci/include/hpx/parcelport_lci/putva/receiver_putva.hpp
@@ -158,8 +158,8 @@ namespace hpx::parcelset::policies::lci {
                 buffer.num_chunks_.second = num_non_zero_copy_chunks;
                 auto& tchunks = buffer.transmission_chunks_;
                 tchunks.resize(num_zero_copy_chunks + num_non_zero_copy_chunks);
-                int tchunks_length = static_cast<int>(tchunks.size() *
-                    sizeof(buffer_type::transmission_chunk_type));
+                size_t tchunks_length = tchunks.size() *
+                    sizeof(buffer_type::transmission_chunk_type);
                 char* piggy_back_tchunk = header_.piggy_back_tchunk();
                 if (piggy_back_tchunk)
                 {
@@ -178,8 +178,7 @@ namespace hpx::parcelset::policies::lci {
                 buffer.chunks_.resize(num_zero_copy_chunks);
                 for (int j = 0; j < num_zero_copy_chunks; ++j)
                 {
-                    std::size_t chunk_size =
-                        buffer.transmission_chunks_[j].second;
+                    size_t chunk_size = buffer.transmission_chunks_[j].second;
                     HPX_ASSERT(iovec.lbuffers[i].length == chunk_size);
                     buffer.chunks_[j] = serialization::create_pointer_chunk(
                         iovec.lbuffers[i].address, chunk_size);
diff --git a/libs/full/parcelport_lci/include/hpx/parcelport_lci/sendrecv/receiver_connection_sendrecv.hpp b/libs/full/parcelport_lci/include/hpx/parcelport_lci/sendrecv/receiver_connection_sendrecv.hpp
index 87fd6a4076c2..67b1cf4fc50a 100644
--- a/libs/full/parcelport_lci/include/hpx/parcelport_lci/sendrecv/receiver_connection_sendrecv.hpp
+++ b/libs/full/parcelport_lci/include/hpx/parcelport_lci/sendrecv/receiver_connection_sendrecv.hpp
@@ -48,7 +48,7 @@ namespace hpx::parcelset::policies::lci {
             rcvd_chunks,
             locked
         };
-        LCI_comp_t unified_recv(void* address, int length);
+        LCI_comp_t unified_recv(void* address, size_t length);
         return_t receive_transmission_chunks();
         return_t receive_data();
         return_t receive_chunks();
diff --git a/libs/full/parcelport_lci/include/hpx/parcelport_lci/sendrecv/sender_connection_sendrecv.hpp b/libs/full/parcelport_lci/include/hpx/parcelport_lci/sendrecv/sender_connection_sendrecv.hpp
index b54ef136ed77..e18b1419b4d6 100644
--- a/libs/full/parcelport_lci/include/hpx/parcelport_lci/sendrecv/sender_connection_sendrecv.hpp
+++ b/libs/full/parcelport_lci/include/hpx/parcelport_lci/sendrecv/sender_connection_sendrecv.hpp
@@ -48,7 +48,7 @@ namespace hpx::parcelset::policies::lci {
             locked,
         };
         return_t send_header();
-        return_t unified_followup_send(void* address, int length);
+        return_t unified_followup_send(void* address, size_t length);
         return_t send_transmission_chunks();
         return_t send_data();
         return_t send_chunks();
diff --git a/libs/full/parcelport_lci/src/putva/sender_connection_putva.cpp b/libs/full/parcelport_lci/src/putva/sender_connection_putva.cpp
index e9da675f29ae..48ceed145eab 100644
--- a/libs/full/parcelport_lci/src/putva/sender_connection_putva.cpp
+++ b/libs/full/parcelport_lci/src/putva/sender_connection_putva.cpp
@@ -120,8 +120,8 @@ namespace hpx::parcelset::policies::lci {
                     std::vector<
                         typename parcel_buffer_type::transmission_chunk_type>&
                         tchunks = buffer_.transmission_chunks_;
-                    int tchunks_length = static_cast<int>(tchunks.size() *
-                        sizeof(parcel_buffer_type::transmission_chunk_type));
+                    size_t tchunks_length = tchunks.size() *
+                        sizeof(parcel_buffer_type::transmission_chunk_type);
                     iovec.lbuffers[i].address = tchunks.data();
                     iovec.lbuffers[i].length = tchunks_length;
                     if (config_t::reg_mem)
diff --git a/libs/full/parcelport_lci/src/sendrecv/receiver_connection_sendrecv.cpp b/libs/full/parcelport_lci/src/sendrecv/receiver_connection_sendrecv.cpp
index d3d6e2180d17..c46be6d9cd19 100644
--- a/libs/full/parcelport_lci/src/sendrecv/receiver_connection_sendrecv.cpp
+++ b/libs/full/parcelport_lci/src/sendrecv/receiver_connection_sendrecv.cpp
@@ -67,8 +67,8 @@ namespace hpx::parcelset::policies::lci {
             buffer.num_chunks_.second = num_non_zero_copy_chunks;
             auto& tchunks = buffer.transmission_chunks_;
             tchunks.resize(num_zero_copy_chunks + num_non_zero_copy_chunks);
-            int tchunks_length = static_cast<int>(tchunks.size() *
-                sizeof(receiver_base::buffer_type::transmission_chunk_type));
+            size_t tchunks_length = tchunks.size() *
+                sizeof(receiver_base::buffer_type::transmission_chunk_type);
             char* piggy_back_tchunk = header_.piggy_back_tchunk();
             if (piggy_back_tchunk)
             {
@@ -135,11 +135,11 @@ namespace hpx::parcelset::policies::lci {
     }
 
     LCI_comp_t receiver_connection_sendrecv::unified_recv(
-        void* address, int length)
+        void* address, size_t length)
     {
         LCI_comp_t completion =
             device_p->completion_manager_p->recv_followup->alloc_completion();
-        if (length <= LCI_MEDIUM_SIZE)
+        if (length <= (size_t) LCI_MEDIUM_SIZE)
         {
             LCI_mbuffer_t mbuffer;
             mbuffer.address = address;
@@ -197,8 +197,8 @@ namespace hpx::parcelset::policies::lci {
         if (need_recv_tchunks)
         {
             auto& tchunks = buffer.transmission_chunks_;
-            int tchunk_length = static_cast<int>(tchunks.size() *
-                sizeof(receiver_base::buffer_type::transmission_chunk_type));
+            size_t tchunk_length = tchunks.size() *
+                sizeof(receiver_base::buffer_type::transmission_chunk_type);
             state.store(connection_state::locked, std::memory_order_relaxed);
             LCI_comp_t completion = unified_recv(tchunks.data(), tchunk_length);
             state.store(next_state, std::memory_order_release);
@@ -221,8 +221,8 @@ namespace hpx::parcelset::policies::lci {
         if (need_recv_data)
         {
             state.store(connection_state::locked, std::memory_order_relaxed);
-            LCI_comp_t completion = unified_recv(
-                buffer.data_.data(), static_cast<int>(buffer.data_.size()));
+            LCI_comp_t completion =
+                unified_recv(buffer.data_.data(), buffer.data_.size());
             state.store(next_state, std::memory_order_release);
             return {false, completion};
         }
@@ -316,8 +316,7 @@ namespace hpx::parcelset::policies::lci {
             HPX_UNUSED(chunk_size);
 
             state.store(connection_state::locked, std::memory_order_relaxed);
-            LCI_comp_t completion =
-                unified_recv(chunk.data(), static_cast<int>(chunk.size()));
+            LCI_comp_t completion = unified_recv(chunk.data(), chunk.size());
             state.store(current_state, std::memory_order_release);
             return {false, completion};
         }
@@ -344,8 +343,7 @@ namespace hpx::parcelset::policies::lci {
             buffer.chunks_[idx] =
                 serialization::create_pointer_chunk(chunk.data(), chunk.size());
             state.store(connection_state::locked, std::memory_order_relaxed);
-            LCI_comp_t completion =
-                unified_recv(chunk.data(), static_cast<int>(chunk.size()));
+            LCI_comp_t completion = unified_recv(chunk.data(), chunk.size());
             state.store(current_state, std::memory_order_release);
             return {false, completion};
         }
diff --git a/libs/full/parcelport_lci/src/sendrecv/sender_connection_sendrecv.cpp b/libs/full/parcelport_lci/src/sendrecv/sender_connection_sendrecv.cpp
index 6979f8b348dc..05a8607b704d 100644
--- a/libs/full/parcelport_lci/src/sendrecv/sender_connection_sendrecv.cpp
+++ b/libs/full/parcelport_lci/src/sendrecv/sender_connection_sendrecv.cpp
@@ -228,9 +228,10 @@ namespace hpx::parcelset::policies::lci {
     }
 
     sender_connection_sendrecv::return_t
-    sender_connection_sendrecv::unified_followup_send(void* address, int length)
+    sender_connection_sendrecv::unified_followup_send(
+        void* address, size_t length)
     {
-        if (length <= LCI_MEDIUM_SIZE)
+        if (length <= (size_t) LCI_MEDIUM_SIZE)
         {
             LCI_mbuffer_t buffer;
             buffer.address = address;
@@ -323,7 +324,7 @@ namespace hpx::parcelset::policies::lci {
 
         std::vector<typename parcel_buffer_type::transmission_chunk_type>&
             tchunks = buffer_.transmission_chunks_;
-        int tchunks_size = (int) tchunks.size() *
+        size_t tchunks_size = tchunks.size() *
             sizeof(parcel_buffer_type::transmission_chunk_type);
         state.store(connection_state::locked, std::memory_order_relaxed);
         auto ret = unified_followup_send(tchunks.data(), tchunks_size);
@@ -389,9 +390,8 @@ namespace hpx::parcelset::policies::lci {
             {
                 state.store(
                     connection_state::locked, std::memory_order_relaxed);
-                auto ret =
-                    unified_followup_send(const_cast<void*>(chunk.data_.cpos_),
-                        static_cast<int>(chunk.size_));
+                auto ret = unified_followup_send(
+                    const_cast<void*>(chunk.data_.cpos_), chunk.size_);
                 if (ret.status == return_status_t::done)
                 {
                     ++send_chunks_idx;