diff --git a/src/sys/driver.c b/src/sys/driver.c
index a9276941..12fffa15 100644
--- a/src/sys/driver.c
+++ b/src/sys/driver.c
@@ -176,6 +176,8 @@ NTSTATUS DriverEntry(
 
 static VOID FspDriverMultiVersionInitialize(VOID)
 {
+    ExInitializeDriverRuntime(DrvRtPoolNxOptIn);
+
     if (RtlIsNtDdiVersionAvailable(NTDDI_WIN7))
     {
         UNICODE_STRING Name;
diff --git a/src/sys/driver.h b/src/sys/driver.h
index fce15d4e..512173b0 100644
--- a/src/sys/driver.h
+++ b/src/sys/driver.h
@@ -19,6 +19,8 @@
 #define WINFSP_SYS_DRIVER_H_INCLUDED
 
 #define WINFSP_SYS_INTERNAL
+
+#define POOL_NX_OPTIN                   1
 #include <ntifs.h>
 #include <ntstrsafe.h>
 #include <wdmsec.h>
diff --git a/src/sys/util.c b/src/sys/util.c
index 379ad22b..c8847188 100644
--- a/src/sys/util.c
+++ b/src/sys/util.c
@@ -851,8 +851,13 @@ NTSTATUS FspSafeMdlCreate(PMDL UserMdl, LOCK_OPERATION Operation, FSP_SAFE_MDL *
 {
     PAGED_CODE();
 
-    NTSTATUS Result;
+    *PSafeMdl = 0;
+
     PVOID VirtualAddress = MmGetSystemAddressForMdlSafe(UserMdl, NormalPagePriority);
+    if (0 == VirtualAddress)
+        return STATUS_INSUFFICIENT_RESOURCES;
+
+    NTSTATUS Result;
     ULONG ByteCount = MmGetMdlByteCount(UserMdl);
     ULONG PageCount = ADDRESS_AND_SIZE_TO_SPAN_PAGES(VirtualAddress, ByteCount);
     FSP_SAFE_MDL *SafeMdl;
@@ -865,8 +870,6 @@ NTSTATUS FspSafeMdlCreate(PMDL UserMdl, LOCK_OPERATION Operation, FSP_SAFE_MDL *
     ASSERT(0 != PageCount);
     ASSERT(FlagOn(UserMdl->MdlFlags, MDL_SOURCE_IS_NONPAGED_POOL | MDL_PAGES_LOCKED));
 
-    *PSafeMdl = 0;
-
     SafeMdl = FspAllocNonPaged(sizeof *SafeMdl);
     if (0 == SafeMdl)
     {
@@ -996,6 +999,9 @@ VOID FspSafeMdlCopyBack(FSP_SAFE_MDL *SafeMdl)
         return;
 
     PVOID VirtualAddress = MmGetSystemAddressForMdlSafe(SafeMdl->UserMdl, NormalPagePriority);
+    if (0 == VirtualAddress)
+        return; /* should never happen, already checked in FspSafeMdlCreate */
+
     ULONG ByteCount = MmGetMdlByteCount(SafeMdl->UserMdl);
     ULONG PageCount = ADDRESS_AND_SIZE_TO_SPAN_PAGES(VirtualAddress, ByteCount);
     ULONG ByteOffsetBgn0, ByteOffsetEnd0, ByteOffsetEnd1;