diff --git a/vpnor/backend.cpp b/vpnor/backend.cpp
index f1b2c63..43591db 100644
--- a/vpnor/backend.cpp
+++ b/vpnor/backend.cpp
@@ -419,6 +419,8 @@
         const pnor_partition& part = priv->vpnor->table->partition(offset);
         if (vpnor_partition_is_readonly(part))
         {
+            MSG_DBG("Try to write read only partition (part=%s, offset=0x%x)\n",
+                    part.data.name, offset);
             return -EPERM;
         }
     }
@@ -462,6 +464,47 @@
     return reset_lpc_memory;
 }
 
+/*
+ * vpnor_align_offset() - Align the offset
+ * @context:    The backend context pointer
+ * @offset:	The flash offset
+ * @window_size:The window size
+ *
+ * Return:      0 on success otherwise negative error code
+ */
+static int vpnor_align_offset(struct backend* backend, uint32_t* offset,
+                              uint32_t window_size)
+{
+    const struct vpnor_data* priv = (const struct vpnor_data*)backend->priv;
+
+    /* Adjust the offset to align with the offset of partition base */
+    try
+    {
+        // Get the base of the partition
+        const pnor_partition& part = priv->vpnor->table->partition(*offset);
+        uint32_t base = part.data.base * VPNOR_ERASE_SIZE;
+
+        // Get the base offset relative to the window_size
+        uint32_t base_offset = base & (window_size - 1);
+
+        // Adjust the offset to align with the base
+        *offset = ((*offset - base_offset) & ~(window_size - 1)) + base_offset;
+        MSG_DBG(
+            "vpnor_align_offset: to @ 0x%.8x(base=0x%.8x base_offset=0x%.8x)\n",
+            *offset, base, base_offset);
+        return 0;
+    }
+    catch (const openpower::virtual_pnor::UnmappedOffset& e)
+    {
+        /*
+         * Writes to unmapped areas are not meaningful, so deny the request.
+         * This removes the ability for a compromised host to abuse unused
+         * space if any data was to be persisted (which it isn't).
+         */
+        return -EACCES;
+    }
+}
+
 static const struct backend_ops vpnor_ops = {
     .init = vpnor_dev_init,
     .free = vpnor_free,
@@ -471,6 +514,7 @@
     .write = vpnor_write,
     .validate = vpnor_validate,
     .reset = vpnor_reset,
+    .align_offset = vpnor_align_offset,
 };
 
 struct backend backend_get_vpnor(void)
diff --git a/vpnor/test/Makefile.am.include b/vpnor/test/Makefile.am.include
index 3e2edaa..71a1517 100644
--- a/vpnor/test/Makefile.am.include
+++ b/vpnor/test/Makefile.am.include
@@ -16,6 +16,14 @@
 	$(PHOSPHOR_LOGGING_LIBS) \
 	$(PHOSPHOR_DBUS_INTERFACES_LIBS)
 
+
+vpnor_test_create_aligned_window_SOURCES = \
+	$(TEST_MOCK_VPNOR_SRCS) \
+	$(TEST_MBOX_VPNOR_INTEG_SRCS) \
+	%reldir%/create_aligned_window.cpp
+vpnor_test_create_aligned_window_LDFLAGS = $(OESDK_TESTCASE_FLAGS)
+vpnor_test_create_aligned_window_LDADD = $(VPNOR_LDADD)
+
 vpnor_test_create_pnor_partition_table_SOURCES = \
 	$(TEST_MOCK_VPNOR_SRCS) \
 	$(TEST_MBOX_VPNOR_INTEG_SRCS) \
@@ -227,6 +235,7 @@
 vpnor_test_force_readonly_toc_LDADD = $(VPNOR_LDADD)
 
 check_PROGRAMS += \
+        %reldir%/create_aligned_window \
 	%reldir%/create_pnor_partition_table \
 	%reldir%/create_read_window_partition_exists \
 	%reldir%/write_prsv \
@@ -260,3 +269,5 @@
 
 XFAIL_TESTS += \
 	%reldir%/write_toc
+
+
diff --git a/vpnor/test/create_aligned_window.cpp b/vpnor/test/create_aligned_window.cpp
new file mode 100644
index 0000000..910e7c5
--- /dev/null
+++ b/vpnor/test/create_aligned_window.cpp
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright (C) 2018 IBM Corp.
+
+#include "config.h"
+
+extern "C" {
+#include "test/mbox.h"
+#include "test/system.h"
+}
+
+#include "vpnor/test/tmpd.hpp"
+
+#include <cassert>
+#include <cstring>
+#include <experimental/filesystem>
+#include <fstream>
+#include <vector>
+
+#include "vpnor/backend.h"
+
+// A read window assumes that the toc is located at offset 0,
+// so create dummy partition at arbitrary offset 0x1000.
+const std::string toc[] = {
+    "partition01=HBB,00001000,00002000,80,ECC,READONLY",
+    "partition05=DJVPD,0x000e5000,0x0022d000,00,ECC,PRESERVED",
+};
+
+static const auto BLOCK_SIZE = 4096;
+static const auto ERASE_SIZE = BLOCK_SIZE;
+static const auto N_WINDOWS = 1;
+static const auto WINDOW_SIZE = 1024 * 1024;
+static const auto MEM_SIZE = WINDOW_SIZE * 3;
+
+static const uint8_t get_info[] = {0x02, 0x00, 0x02, 0x00, 0x00, 0x00,
+                                   0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                   0x00, 0x00, 0x00, 0x00};
+
+// Used to check the alignment
+static const uint8_t create_read_window1[] = {
+    0x04, 0x01, 0xe7, 0x00, 0x01, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+
+static const uint8_t response1[] = {0x04, 0x01, 0x00, 0xfd, 0x00, 0x01, 0xe5,
+                                    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01};
+
+static const uint8_t create_read_window2[] = {
+    0x04, 0x02, 0xe5, 0x01, 0x01, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+
+static const uint8_t response2[] = {0x04, 0x02, 0x00, 0xfd, 0x48, 0x00, 0xe5,
+                                    0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01};
+
+namespace test = openpower::virtual_pnor::test;
+
+int main()
+{
+    struct mbox_context* ctx;
+
+    system_set_reserved_size(MEM_SIZE);
+    system_set_mtd_sizes(MEM_SIZE, ERASE_SIZE);
+
+    ctx = mbox_create_frontend_context(N_WINDOWS, WINDOW_SIZE);
+
+    test::VpnorRoot root(&ctx->backend, toc, BLOCK_SIZE);
+
+    int rc = mbox_command_dispatch(ctx, get_info, sizeof(get_info));
+    assert(rc == 1);
+
+    // send the request for partition5
+    rc = mbox_command_dispatch(ctx, create_read_window1,
+                               sizeof(create_read_window1));
+    assert(rc == 1);
+    rc = mbox_cmp(ctx, response1, sizeof(response1));
+    assert(rc == 0);
+
+    // send the request for partition5
+    rc = mbox_command_dispatch(ctx, create_read_window2,
+                               sizeof(create_read_window2));
+    assert(rc == 1);
+    rc = mbox_cmp(ctx, response2, sizeof(response2));
+    assert(rc == 0);
+
+    return rc;
+}