diff --git a/reactos/ntoskrnl/mm/anonmem.c b/reactos/ntoskrnl/mm/anonmem.c
index 0940db22ffc..659be426093 100644
--- a/reactos/ntoskrnl/mm/anonmem.c
+++ b/reactos/ntoskrnl/mm/anonmem.c
@@ -183,7 +183,7 @@ MmNotPresentFaultVirtualMemory(PMMSUPPORT AddressSpace,
     * address space when another thread could load the page so we check
     * that.
     */
-    if (MmIsPagePresent(NULL, Address))
+    if (MmIsPagePresent(Process, Address))
     {
         return(STATUS_SUCCESS);
     }
@@ -301,7 +301,7 @@ MmNotPresentFaultVirtualMemory(PMMSUPPORT AddressSpace,
     /*
     * Handle swapped out pages.
     */
-    if (MmIsPageSwapEntry(NULL, Address))
+    if (MmIsPageSwapEntry(Process, Address))
     {
         SWAPENTRY SwapEntry;
 
@@ -327,7 +327,7 @@ MmNotPresentFaultVirtualMemory(PMMSUPPORT AddressSpace,
     {
         MmUnlockAddressSpace(AddressSpace);
         Status = MmCreateVirtualMapping(Process,
-            Address,
+            (PVOID)PAGE_ROUND_DOWN(Address),
             Region->Protect,
             &Page,
             1);
diff --git a/reactos/ntoskrnl/mm/freelist.c b/reactos/ntoskrnl/mm/freelist.c
index c4cf0e2987f..f8efc073964 100644
--- a/reactos/ntoskrnl/mm/freelist.c
+++ b/reactos/ntoskrnl/mm/freelist.c
@@ -92,6 +92,7 @@ MmInsertLRULastUserPage(PFN_NUMBER Pfn)
     /* Set the page as a user page */
     ASSERT(Pfn != 0);
     ASSERT_IS_ROS_PFN(MiGetPfnEntry(Pfn));
+    ASSERT(!RtlCheckBit(&MiUserPfnBitMap, (ULONG)Pfn));
     OldIrql = KeAcquireQueuedSpinLock(LockQueuePfnLock);
     RtlSetBit(&MiUserPfnBitMap, (ULONG)Pfn);
     KeReleaseQueuedSpinLock(LockQueuePfnLock, OldIrql);
@@ -123,6 +124,7 @@ MmRemoveLRUUserPage(PFN_NUMBER Page)
     /* Unset the page as a user page */
     ASSERT(Page != 0);
     ASSERT_IS_ROS_PFN(MiGetPfnEntry(Page));
+    ASSERT(RtlCheckBit(&MiUserPfnBitMap, (ULONG)Page));
     RtlClearBit(&MiUserPfnBitMap, (ULONG)Page);
 }
 
diff --git a/reactos/ntoskrnl/mm/marea.c b/reactos/ntoskrnl/mm/marea.c
index fb3265e63a8..fe6717131be 100644
--- a/reactos/ntoskrnl/mm/marea.c
+++ b/reactos/ntoskrnl/mm/marea.c
@@ -893,7 +893,7 @@ MmCreateMemoryArea(PMMSUPPORT AddressSpace,
    Granularity = (MEMORY_AREA_VIRTUAL_MEMORY == Type ? MM_VIRTMEM_GRANULARITY : PAGE_SIZE);
    if ((*BaseAddress) == 0 && !FixedAddress)
    {
-      tmpLength = PAGE_ROUND_UP(Length);
+      tmpLength = (ULONG_PTR)MM_ROUND_UP(Length, Granularity);
       *BaseAddress = MmFindGap(AddressSpace,
                                tmpLength,
                                Granularity,
@@ -908,6 +908,7 @@ MmCreateMemoryArea(PMMSUPPORT AddressSpace,
    {
       tmpLength = Length + ((ULONG_PTR) *BaseAddress
                          - (ULONG_PTR) MM_ROUND_DOWN(*BaseAddress, Granularity));
+      tmpLength = (ULONG_PTR)MM_ROUND_UP(tmpLength, Granularity);
       *BaseAddress = MM_ROUND_DOWN(*BaseAddress, Granularity);
 
       if (!MmGetAddressSpaceOwner(AddressSpace) && *BaseAddress < MmSystemRangeStart)
@@ -986,6 +987,8 @@ MmMapMemoryArea(PVOID BaseAddress,
 {
    ULONG i;
    NTSTATUS Status;
+   
+   ASSERT(((ULONG_PTR)BaseAddress % PAGE_SIZE) == 0);
 
    for (i = 0; i < PAGE_ROUND_UP(Length) / PAGE_SIZE; i++)
    {
diff --git a/reactos/ntoskrnl/mm/pagefile.c b/reactos/ntoskrnl/mm/pagefile.c
index 0a6be61416e..987e798f67c 100644
--- a/reactos/ntoskrnl/mm/pagefile.c
+++ b/reactos/ntoskrnl/mm/pagefile.c
@@ -113,7 +113,7 @@ static PFN_COUNT MiReservedSwapPages;
  */
 #define FILE_FROM_ENTRY(i) ((i) & 0x0f)
 #define OFFSET_FROM_ENTRY(i) ((i) >> 11)
-#define ENTRY_FROM_FILE_OFFSET(i, j) ((i) | (j) << 11 | 0x400)
+#define ENTRY_FROM_FILE_OFFSET(i, j) ((i) | ((j) << 11) | 0x400)
 
 static BOOLEAN MmSwapSpaceMessage = FALSE;