diff --git a/main.cpp b/main.cpp
index 3130eec..9c0c40c 100644
--- a/main.cpp
+++ b/main.cpp
@@ -36,10 +36,14 @@
 FileHandler staticLayoutHandler(STATIC_HANDLER_STAGED_NAME);
 FileHandler ubitarballHandler(TARBALL_STAGED_NAME);
 
+/* The maximum external buffer size we expect is 64KB. */
+static constexpr size_t memoryRegionSize = 64 * 1024UL;
+
 #ifdef ENABLE_LPC_BRIDGE
 #if defined(ASPEED_LPC)
-LpcDataHandler lpcDataHandler(MAPPED_ADDRESS,
-                              LpcMapperAspeed::createAspeedMapper());
+LpcDataHandler
+    lpcDataHandler(MAPPED_ADDRESS,
+                   LpcMapperAspeed::createAspeedMapper(memoryRegionSize));
 #elif defined(NUVOTON_LPC)
 LpcDataHandler lpcDataHandler(MAPPED_ADDRESS,
                               LpcMapperNuvoton::createNuvotonMapper());