diff --git a/src/core/iomgr/tcp_windows.c b/src/core/iomgr/tcp_windows.c
index b768bc89b62..6915cb2f493 100644
--- a/src/core/iomgr/tcp_windows.c
+++ b/src/core/iomgr/tcp_windows.c
@@ -273,6 +273,7 @@ static void win_write(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
   WSABUF local_buffers[16];
   WSABUF *allocated = NULL;
   WSABUF *buffers = local_buffers;
+  size_t len;
 
   if (tcp->shutting_down) {
     grpc_exec_ctx_enqueue(exec_ctx, cb, 0);
@@ -281,15 +282,16 @@ static void win_write(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
 
   tcp->write_cb = cb;
   tcp->write_slices = slices;
-  GPR_ASSERT(tcp->write_slices->count <= UINT32_MAX);
+  GPR_ASSERT(tcp->write_slices->count <= UINT_MAX);
   if (tcp->write_slices->count > GPR_ARRAY_SIZE(local_buffers)) {
     buffers = (WSABUF *)gpr_malloc(sizeof(WSABUF) * tcp->write_slices->count);
     allocated = buffers;
   }
 
   for (i = 0; i < tcp->write_slices->count; i++) {
-    GPR_ASSERT(GPR_SLICE_LENGTH(tcp->write_slices->slices[i]) <= UINT32_MAX);
-    buffers[i].len = (ULONG) GPR_SLICE_LENGTH(tcp->write_slices->slices[i]);
+    len = GPR_SLICE_LENGTH(tcp->write_slices->slices[i]);
+    GPR_ASSERT(len <= ULONG_MAX);
+    buffers[i].len = (ULONG) len;
     buffers[i].buf = (char *)GPR_SLICE_START_PTR(tcp->write_slices->slices[i]);
   }