diff --git a/reactos/boot/freeldr/freeldr/arcemul/mm.c b/reactos/boot/freeldr/freeldr/arcemul/mm.c
index 697481af9ff..0a0472f9f74 100644
--- a/reactos/boot/freeldr/freeldr/arcemul/mm.c
+++ b/reactos/boot/freeldr/freeldr/arcemul/mm.c
@@ -34,8 +34,8 @@ static const MEMORY_DESCRIPTOR_INT MemoryDescriptors[] =
 
 #endif
 };
-MEMORY_DESCRIPTOR*
-ArcGetMemoryDescriptor(MEMORY_DESCRIPTOR* Current)
+const MEMORY_DESCRIPTOR*
+ArcGetMemoryDescriptor(const MEMORY_DESCRIPTOR* Current)
 {
     MEMORY_DESCRIPTOR_INT* CurrentDescriptor;
     BIOS_MEMORY_MAP BiosMemoryMap[32];
@@ -114,7 +114,7 @@ ArcGetMemoryDescriptor(MEMORY_DESCRIPTOR* Current)
             //
             // Return first fixed memory descriptor
             //
-            return (MEMORY_DESCRIPTOR*)&MemoryDescriptors[0].m;
+            return &MemoryDescriptors[0].m;
         }
         else
         {
@@ -141,7 +141,7 @@ ArcGetMemoryDescriptor(MEMORY_DESCRIPTOR* Current)
             //
             // Return first fixed memory descriptor
             //
-            return (MEMORY_DESCRIPTOR*)&MemoryDescriptors[0].m;
+            return &MemoryDescriptors[0].m;
         }
         else
         {
@@ -161,7 +161,7 @@ ArcGetMemoryDescriptor(MEMORY_DESCRIPTOR* Current)
             //
             // Return next fixed descriptor
             //
-            return (MEMORY_DESCRIPTOR*)&MemoryDescriptors[CurrentDescriptor->Index + 1].m;
+            return &MemoryDescriptors[CurrentDescriptor->Index + 1].m;
         }
         else
         {
diff --git a/reactos/boot/freeldr/freeldr/include/arcemul.h b/reactos/boot/freeldr/freeldr/include/arcemul.h
index 45c34ab04b3..2d6a450d2ca 100644
--- a/reactos/boot/freeldr/freeldr/include/arcemul.h
+++ b/reactos/boot/freeldr/freeldr/include/arcemul.h
@@ -35,8 +35,8 @@ ArcGetConfigurationData(
     CONFIGURATION_COMPONENT* Component);
 
 /* mm.c */
-MEMORY_DESCRIPTOR*
-ArcGetMemoryDescriptor(MEMORY_DESCRIPTOR* Current);
+const MEMORY_DESCRIPTOR*
+ArcGetMemoryDescriptor(const MEMORY_DESCRIPTOR* Current);
 
 /* time.c */
 TIMEINFO* ArcGetTime(VOID);
diff --git a/reactos/boot/freeldr/freeldr/include/machine.h b/reactos/boot/freeldr/freeldr/include/machine.h
index ba2be4fdf6a..2ff379368ec 100644
--- a/reactos/boot/freeldr/freeldr/include/machine.h
+++ b/reactos/boot/freeldr/freeldr/include/machine.h
@@ -92,7 +92,6 @@ VOID MachVideoSetPaletteColor(UCHAR Color, UCHAR Red, UCHAR Green, UCHAR Blue);
 VOID MachVideoGetPaletteColor(UCHAR Color, UCHAR *Red, UCHAR *Green, UCHAR *Blue);
 VOID MachVideoSync(VOID);
 VOID MachBeep(VOID);
-MEMORY_DESCRIPTOR* ArcGetMemoryDescriptor(MEMORY_DESCRIPTOR* Current);
 BOOLEAN MachDiskGetBootPath(char *BootPath, unsigned Size);
 BOOLEAN MachDiskNormalizeSystemPath(char *SystemPath, unsigned Size);
 BOOLEAN MachDiskReadLogicalSectors(ULONG DriveNumber, ULONGLONG SectorNumber, ULONG SectorCount, PVOID Buffer);
diff --git a/reactos/boot/freeldr/freeldr/include/mm.h b/reactos/boot/freeldr/freeldr/include/mm.h
index a7840e37791..7640498344e 100644
--- a/reactos/boot/freeldr/freeldr/include/mm.h
+++ b/reactos/boot/freeldr/freeldr/include/mm.h
@@ -42,6 +42,7 @@ typedef struct
 #define MM_PAGE_SIZE	4096
 #define MM_PAGE_MASK	0xFFF
 #define MM_PAGE_SHIFT	12
+#define MM_MAX_PAGE	    0xFFFFF
 
 #define MM_SIZE_TO_PAGES(a)  \
 	( ((a) >> MM_PAGE_SHIFT) + ((a) & MM_PAGE_MASK ? 1 : 0) )
@@ -53,6 +54,7 @@ typedef struct
 #define MM_PAGE_SIZE	4096
 #define MM_PAGE_MASK	0xFFF
 #define MM_PAGE_SHIFT	12
+#define MM_MAX_PAGE	    0xFFFFFFFFFFFFF
 
 #define MM_SIZE_TO_PAGES(a)  \
 	( ((a) >> MM_PAGE_SHIFT) + ((a) & MM_PAGE_MASK ? 1 : 0) )
diff --git a/reactos/boot/freeldr/freeldr/mm/meminit.c b/reactos/boot/freeldr/freeldr/mm/meminit.c
index 3cafb3f6c8f..e8e399bcf3d 100644
--- a/reactos/boot/freeldr/freeldr/mm/meminit.c
+++ b/reactos/boot/freeldr/freeldr/mm/meminit.c
@@ -57,7 +57,7 @@ extern ULONG_PTR	MmHeapStart;
 BOOLEAN MmInitializeMemoryManager(VOID)
 {
 #if DBG
-	MEMORY_DESCRIPTOR* MemoryDescriptor = NULL;
+	const MEMORY_DESCRIPTOR* MemoryDescriptor = NULL;
 #endif
 
 	DPRINTM(DPRINT_MEMORY, "Initializing Memory Manager.\n");
@@ -158,7 +158,7 @@ ULONG MmGetPageNumberFromAddress(PVOID Address)
 
 ULONG MmGetAddressablePageCountIncludingHoles(VOID)
 {
-    MEMORY_DESCRIPTOR* MemoryDescriptor = NULL;
+    const MEMORY_DESCRIPTOR* MemoryDescriptor = NULL;
     ULONG PageCount;
 
     //
@@ -197,7 +197,7 @@ ULONG MmGetAddressablePageCountIncludingHoles(VOID)
 
 PVOID MmFindLocationForPageLookupTable(ULONG TotalPageCount)
 {
-    MEMORY_DESCRIPTOR* MemoryDescriptor = NULL;
+    const MEMORY_DESCRIPTOR* MemoryDescriptor = NULL;
     ULONG PageLookupTableSize;
     ULONG PageLookupTablePages;
     ULONG PageLookupTableStartPage = 0;
@@ -247,6 +247,17 @@ PVOID MmFindLocationForPageLookupTable(ULONG TotalPageCount)
             continue;
         }
 
+        //
+        // Can we use this address?
+        //
+        if (MemoryDescriptor->BasePage >= MM_MAX_PAGE)
+        {
+            //
+            // No. Process next descriptor
+            //
+            continue;
+        }
+
         //
         // Memory block is more suitable than the previous one
         //
@@ -263,7 +274,7 @@ PVOID MmFindLocationForPageLookupTable(ULONG TotalPageCount)
 
 VOID MmInitPageLookupTable(PVOID PageLookupTable, ULONG TotalPageCount)
 {
-    MEMORY_DESCRIPTOR* MemoryDescriptor = NULL;
+    const MEMORY_DESCRIPTOR* MemoryDescriptor = NULL;
     TYPE_OF_MEMORY MemoryMapPageAllocated;
     ULONG PageLookupTableStartPage;
     ULONG PageLookupTablePageCount;
diff --git a/reactos/boot/freeldr/freeldr/windows/wlmemory.c b/reactos/boot/freeldr/freeldr/windows/wlmemory.c
index bfa68ab904e..bfb46abebd6 100644
--- a/reactos/boot/freeldr/freeldr/windows/wlmemory.c
+++ b/reactos/boot/freeldr/freeldr/windows/wlmemory.c
@@ -139,9 +139,10 @@ MempAddMemoryBlock(IN OUT PLOADER_PARAMETER_BLOCK LoaderBlock,
 	BOOLEAN Status;
 
 	//
-	// Check for some weird stuff at the top
+	// Check for memory block after 4GB - we don't support it yet
+	// Note: Even last page before 4GB limit is not supported
 	//
-	if (BasePage + PageCount > 0xF0000)
+	if (BasePage >= MM_MAX_PAGE)
 	{
 		//
 		// Just skip this, without even adding to MAD list
@@ -149,6 +150,17 @@ MempAddMemoryBlock(IN OUT PLOADER_PARAMETER_BLOCK LoaderBlock,
 		return;
 	}
 
+    //
+    // Check if last page is after 4GB limit and shorten this block if needed
+    //
+    if (BasePage + PageCount > MM_MAX_PAGE)
+    {
+        //
+        // shorten this block
+        //
+        PageCount = MM_MAX_PAGE - BasePage;
+    }
+
 	//
 	// Set Base page, page count and type
 	//
@@ -255,7 +267,7 @@ WinLdrTurnOnPaging(IN OUT PLOADER_PARAMETER_BLOCK LoaderBlock,
 
 	// Calculate parameters of the memory map
 	MemoryMapStartPage = (ULONG_PTR)MemoryMap >> MM_PAGE_SHIFT;
-	MemoryMapSizeInPages = NoEntries * sizeof(PAGE_LOOKUP_TABLE_ITEM);
+	MemoryMapSizeInPages = (NoEntries * sizeof(PAGE_LOOKUP_TABLE_ITEM) + MM_PAGE_SIZE - 1) / MM_PAGE_SIZE;
 
 	DPRINTM(DPRINT_WINDOWS, "Got memory map with %d entries\n", NoEntries);