diff --git a/rostests/apitests/ntdll/RtlBitmap.c b/rostests/apitests/ntdll/RtlBitmap.c
index a3b221ecdb6..c01795db475 100644
--- a/rostests/apitests/ntdll/RtlBitmap.c
+++ b/rostests/apitests/ntdll/RtlBitmap.c
@@ -2,8 +2,56 @@
 #include <apitest.h>
 
 #define WIN32_NO_STATUS
+#include <ndk/mmfuncs.h>
 #include <ndk/rtlfuncs.h>
 
+static
+PVOID
+AllocateGuarded(
+    _In_ SIZE_T SizeRequested)
+{
+    NTSTATUS Status;
+    SIZE_T Size = PAGE_ROUND_UP(SizeRequested + PAGE_SIZE);
+    PVOID VirtualMemory = NULL;
+    PCHAR StartOfBuffer;
+
+    Status = NtAllocateVirtualMemory(NtCurrentProcess(), &VirtualMemory, 0, &Size, MEM_RESERVE, PAGE_NOACCESS);
+
+    if (!NT_SUCCESS(Status))
+        return NULL;
+
+    Size -= PAGE_SIZE;
+    if (Size)
+    {
+        Status = NtAllocateVirtualMemory(NtCurrentProcess(), &VirtualMemory, 0, &Size, MEM_COMMIT, PAGE_READWRITE);
+        if (!NT_SUCCESS(Status))
+        {
+            Size = 0;
+            Status = NtFreeVirtualMemory(NtCurrentProcess(), &VirtualMemory, &Size, MEM_RELEASE);
+            ok(Status == STATUS_SUCCESS, "Status = %lx\n", Status);
+            return NULL;
+        }
+    }
+
+    StartOfBuffer = VirtualMemory;
+    StartOfBuffer += Size - SizeRequested;
+
+    return StartOfBuffer;
+}
+
+static
+VOID
+FreeGuarded(
+    _In_ PVOID Pointer)
+{
+    NTSTATUS Status;
+    PVOID VirtualMemory = (PVOID)PAGE_ROUND_DOWN((SIZE_T)Pointer);
+    SIZE_T Size = 0;
+
+    Status = NtFreeVirtualMemory(NtCurrentProcess(), &VirtualMemory, &Size, MEM_RELEASE);
+    ok(Status == STATUS_SUCCESS, "Status = %lx\n", Status);
+}
+
 void
 Test_RtlFindMostSignificantBit(void)
 {
@@ -65,130 +113,155 @@ void
 Test_RtlClearAllBits(void)
 {
     RTL_BITMAP BitMapHeader;
-    ULONG Buffer[2];
+    ULONG *Buffer;
+    ULONG BufferSize = 2 * sizeof(*Buffer);
 
+    Buffer = AllocateGuarded(BufferSize);
     RtlInitializeBitMap(&BitMapHeader, Buffer, 19);
-    memset(Buffer, 0xcc, sizeof(Buffer));
+    memset(Buffer, 0xcc, BufferSize);
     RtlClearAllBits(&BitMapHeader);
     ok_hex(Buffer[0], 0x00000000);
     ok_hex(Buffer[1], 0xcccccccc);
 
     RtlInitializeBitMap(&BitMapHeader, Buffer, 0);
-    memset(Buffer, 0xcc, sizeof(Buffer));
+    memset(Buffer, 0xcc, BufferSize);
     RtlClearAllBits(&BitMapHeader);
     ok_hex(Buffer[0], 0xcccccccc);
     ok_hex(Buffer[1], 0xcccccccc);
+
+    RtlInitializeBitMap(&BitMapHeader, Buffer, 64);
+    memset(Buffer, 0xcc, BufferSize);
+    RtlClearAllBits(&BitMapHeader);
+    ok_hex(Buffer[0], 0x00000000);
+    ok_hex(Buffer[1], 0x00000000);
+    FreeGuarded(Buffer);
 }
 
 void
 Test_RtlSetAllBits(void)
 {
     RTL_BITMAP BitMapHeader;
-    ULONG Buffer[2];
+    ULONG *Buffer;
+    ULONG BufferSize = 2 * sizeof(*Buffer);
 
+    Buffer = AllocateGuarded(BufferSize);
     RtlInitializeBitMap(&BitMapHeader, Buffer, 19);
-    memset(Buffer, 0xcc, sizeof(Buffer));
+    memset(Buffer, 0xcc, BufferSize);
     RtlSetAllBits(&BitMapHeader);
     ok_hex(Buffer[0], 0xffffffff);
     ok_hex(Buffer[1], 0xcccccccc);
 
     RtlInitializeBitMap(&BitMapHeader, Buffer, 0);
-    memset(Buffer, 0xcc, sizeof(Buffer));
+    memset(Buffer, 0xcc, BufferSize);
     RtlSetAllBits(&BitMapHeader);
     ok_hex(Buffer[0], 0xcccccccc);
     ok_hex(Buffer[1], 0xcccccccc);
+
+    RtlInitializeBitMap(&BitMapHeader, Buffer, 64);
+    memset(Buffer, 0xcc, BufferSize);
+    RtlSetAllBits(&BitMapHeader);
+    ok_hex(Buffer[0], 0xffffffff);
+    ok_hex(Buffer[1], 0xffffffff);
+    FreeGuarded(Buffer);
 }
 
 void
 Test_RtlClearBits(void)
 {
     RTL_BITMAP BitMapHeader;
-    ULONG Buffer[2];
+    ULONG *Buffer;
+    ULONG BufferSize = 2 * sizeof(*Buffer);
 
+    Buffer = AllocateGuarded(BufferSize);
     RtlInitializeBitMap(&BitMapHeader, Buffer, 19);
 
-    memset(Buffer, 0xff, sizeof(Buffer));
+    memset(Buffer, 0xff, BufferSize);
     RtlClearBits(&BitMapHeader, 0, 0);
     ok_hex(Buffer[0], 0xffffffff);
     ok_hex(Buffer[1], 0xffffffff);
 
-    memset(Buffer, 0xff, sizeof(Buffer));
+    memset(Buffer, 0xff, BufferSize);
     RtlClearBits(&BitMapHeader, 0, 1);
     ok_hex(Buffer[0], 0xfffffffe);
     ok_hex(Buffer[1], 0xffffffff);
 
-    memset(Buffer, 0xff, sizeof(Buffer));
+    memset(Buffer, 0xff, BufferSize);
     RtlClearBits(&BitMapHeader, 21, 1);
     ok_hex(Buffer[0], 0xffdfffff);
     ok_hex(Buffer[1], 0xffffffff);
 
-    memset(Buffer, 0xff, sizeof(Buffer));
+    memset(Buffer, 0xff, BufferSize);
     RtlClearBits(&BitMapHeader, 7, 9);
     ok_hex(Buffer[0], 0xffff007f);
     ok_hex(Buffer[1], 0xffffffff);
 
-    memset(Buffer, 0xff, sizeof(Buffer));
+    memset(Buffer, 0xff, BufferSize);
     RtlClearBits(&BitMapHeader, 13, 22);
     ok_hex(Buffer[0], 0x00001fff);
     ok_hex(Buffer[1], 0xfffffff8);
 
-    memset(Buffer, 0xcc, sizeof(Buffer));
+    memset(Buffer, 0xcc, BufferSize);
     RtlClearBits(&BitMapHeader, 3, 6);
     RtlClearBits(&BitMapHeader, 11, 5);
     RtlClearBits(&BitMapHeader, 21, 7);
     RtlClearBits(&BitMapHeader, 37, 4);
     ok_hex(Buffer[0], 0xc00c0404);
     ok_hex(Buffer[1], 0xcccccc0c);
+    FreeGuarded(Buffer);
 }
 
 void
 Test_RtlSetBits(void)
 {
     RTL_BITMAP BitMapHeader;
-    ULONG Buffer[2];
+    ULONG *Buffer;
+    ULONG BufferSize = 2 * sizeof(*Buffer);
 
+    Buffer = AllocateGuarded(BufferSize);
     RtlInitializeBitMap(&BitMapHeader, Buffer, 19);
 
-    memset(Buffer, 0x00, sizeof(Buffer));
+    memset(Buffer, 0x00, BufferSize);
     RtlSetBits(&BitMapHeader, 0, 0);
     ok_hex(Buffer[0], 0x00000000);
     ok_hex(Buffer[1], 0x00000000);
 
-    memset(Buffer, 0x00, sizeof(Buffer));
+    memset(Buffer, 0x00, BufferSize);
     RtlSetBits(&BitMapHeader, 0, 1);
     ok_hex(Buffer[0], 0x00000001);
     ok_hex(Buffer[1], 0x00000000);
 
-    memset(Buffer, 0x00, sizeof(Buffer));
+    memset(Buffer, 0x00, BufferSize);
     RtlSetBits(&BitMapHeader, 21, 1);
     ok_hex(Buffer[0], 0x00200000);
     ok_hex(Buffer[1], 0x00000000);
 
-    memset(Buffer, 0x00, sizeof(Buffer));
+    memset(Buffer, 0x00, BufferSize);
     RtlSetBits(&BitMapHeader, 7, 9);
     ok_hex(Buffer[0], 0x0000ff80);
     ok_hex(Buffer[1], 0x00000000);
 
-    memset(Buffer, 0x00, sizeof(Buffer));
+    memset(Buffer, 0x00, BufferSize);
     RtlSetBits(&BitMapHeader, 13, 22);
     ok_hex(Buffer[0], 0xffffe000);
     ok_hex(Buffer[1], 0x00000007);
 
-    memset(Buffer, 0xcc, sizeof(Buffer));
+    memset(Buffer, 0xcc, BufferSize);
     RtlSetBits(&BitMapHeader, 3, 6);
     RtlSetBits(&BitMapHeader, 11, 5);
     RtlSetBits(&BitMapHeader, 21, 7);
     RtlSetBits(&BitMapHeader, 37, 4);
     ok_hex(Buffer[0], 0xcfecfdfc);
     ok_hex(Buffer[1], 0xcccccdec);
+    FreeGuarded(Buffer);
 }
 
 void
 Test_RtlAreBitsClear(void)
 {
     RTL_BITMAP BitMapHeader;
-    ULONG Buffer[2];
+    ULONG *Buffer;
 
+    Buffer = AllocateGuarded(2 * sizeof(*Buffer));
     RtlInitializeBitMap(&BitMapHeader, Buffer, 19);
     Buffer[0] = 0x00ff00ff;
     Buffer[1] = 0xc0cfc0cf;
@@ -204,14 +277,18 @@ Test_RtlAreBitsClear(void)
     ok_hex(RtlAreBitsClear(&BitMapHeader, 24, 7), TRUE);
     ok_hex(RtlAreBitsClear(&BitMapHeader, 24, 8), FALSE);
 
+    RtlInitializeBitMap(&BitMapHeader, Buffer, 64);
+    ok_hex(RtlAreBitsClear(&BitMapHeader, 60, 4), FALSE);
+    FreeGuarded(Buffer);
 }
 
 void
 Test_RtlAreBitsSet(void)
 {
     RTL_BITMAP BitMapHeader;
-    ULONG Buffer[2];
+    ULONG *Buffer;
 
+    Buffer = AllocateGuarded(2 * sizeof(*Buffer));
     RtlInitializeBitMap(&BitMapHeader, Buffer, 19);
     Buffer[0] = 0xff00ff00;
     Buffer[1] = 0x3F303F30;
@@ -227,14 +304,18 @@ Test_RtlAreBitsSet(void)
     ok_hex(RtlAreBitsSet(&BitMapHeader, 24, 7), TRUE);
     ok_hex(RtlAreBitsSet(&BitMapHeader, 24, 8), FALSE);
 
+    RtlInitializeBitMap(&BitMapHeader, Buffer, 64);
+    ok_hex(RtlAreBitsSet(&BitMapHeader, 60, 4), FALSE);
+    FreeGuarded(Buffer);
 }
 
 void
 Test_RtlNumberOfSetBits(void)
 {
     RTL_BITMAP BitMapHeader;
-    ULONG Buffer[2];
+    ULONG *Buffer;
 
+    Buffer = AllocateGuarded(2 * sizeof(*Buffer));
     Buffer[0] = 0xff00ff0f;
     Buffer[1] = 0x3F303F30;
 
@@ -249,14 +330,19 @@ Test_RtlNumberOfSetBits(void)
 
     RtlInitializeBitMap(&BitMapHeader, Buffer, 56);
     ok_int(RtlNumberOfSetBits(&BitMapHeader), 30);
+
+    RtlInitializeBitMap(&BitMapHeader, Buffer, 64);
+    ok_int(RtlNumberOfSetBits(&BitMapHeader), 36);
+    FreeGuarded(Buffer);
 }
 
 void
 Test_RtlNumberOfClearBits(void)
 {
     RTL_BITMAP BitMapHeader;
-    ULONG Buffer[2];
+    ULONG *Buffer;
 
+    Buffer = AllocateGuarded(2 * sizeof(*Buffer));
     Buffer[0] = 0xff00fff0;
     Buffer[1] = 0x3F303F30;
 
@@ -271,14 +357,19 @@ Test_RtlNumberOfClearBits(void)
 
     RtlInitializeBitMap(&BitMapHeader, Buffer, 56);
     ok_int(RtlNumberOfClearBits(&BitMapHeader), 26);
+
+    RtlInitializeBitMap(&BitMapHeader, Buffer, 64);
+    ok_int(RtlNumberOfClearBits(&BitMapHeader), 28);
+    FreeGuarded(Buffer);
 }
 
 void
 Test_RtlFindClearBits(void)
 {
     RTL_BITMAP BitMapHeader;
-    ULONG Buffer[2];
+    ULONG *Buffer;
 
+    Buffer = AllocateGuarded(2 * sizeof(*Buffer));
     Buffer[0] = 0x060F874D;
     Buffer[1] = 0x3F303F30;
 
@@ -314,14 +405,20 @@ Test_RtlFindClearBits(void)
     ok_int(RtlFindClearBits(&BitMapHeader, 4, 32), 11);
     ok_int(RtlFindClearBits(&BitMapHeader, 5, 32), 20);
 
+    RtlInitializeBitMap(&BitMapHeader, Buffer, 64);
+    ok_int(RtlFindClearBits(&BitMapHeader, 5, 64), 20);
+    ok_int(RtlFindClearBits(&BitMapHeader, 9, 28), 27);
+    ok_int(RtlFindClearBits(&BitMapHeader, 10, 0), -1);
+    FreeGuarded(Buffer);
 }
 
 void
 Test_RtlFindSetBits(void)
 {
     RTL_BITMAP BitMapHeader;
-    ULONG Buffer[2];
+    ULONG *Buffer;
 
+    Buffer = AllocateGuarded(2 * sizeof(*Buffer));
     Buffer[0] = 0xF9F078B2;
     Buffer[1] = 0x3F303F30;
 
@@ -356,14 +453,20 @@ Test_RtlFindSetBits(void)
     ok_int(RtlFindSetBits(&BitMapHeader, 4, 32), 11);
     ok_int(RtlFindSetBits(&BitMapHeader, 5, 32), 20);
 
+    RtlInitializeBitMap(&BitMapHeader, Buffer, 64);
+    ok_int(RtlFindSetBits(&BitMapHeader, 5, 64), 20);
+    ok_int(RtlFindSetBits(&BitMapHeader, 6, 57), 40);
+    ok_int(RtlFindSetBits(&BitMapHeader, 7, 0), -1);
+    FreeGuarded(Buffer);
 }
 
 void
 Test_RtlFindClearBitsAndSet(void)
 {
     RTL_BITMAP BitMapHeader;
-    ULONG Buffer[2];
+    ULONG *Buffer;
 
+    Buffer = AllocateGuarded(2 * sizeof(*Buffer));
     Buffer[0] = 0x060F874D;
     Buffer[1] = 0x3F303F30;
 
@@ -401,14 +504,16 @@ Test_RtlFindClearBitsAndSet(void)
     ok_hex(Buffer[0], 0x6ff9f4d);
     ok_int(RtlFindClearBitsAndSet(&BitMapHeader, 2, 12), 13);
     ok_hex(Buffer[0], 0x6ffff4d);
+    FreeGuarded(Buffer);
 }
 
 void
 Test_RtlFindSetBitsAndClear(void)
 {
     RTL_BITMAP BitMapHeader;
-    ULONG Buffer[2];
+    ULONG *Buffer;
 
+    Buffer = AllocateGuarded(2 * sizeof(*Buffer));
     Buffer[0] = 0xF9F078B2;
     Buffer[1] = 0x3F303F30;
 
@@ -446,16 +551,17 @@ Test_RtlFindSetBitsAndClear(void)
     ok_hex(Buffer[0], 0xf90060b2);
     ok_int(RtlFindSetBitsAndClear(&BitMapHeader, 2, 12), 13);
     ok_hex(Buffer[0], 0xf90000b2);
-
+    FreeGuarded(Buffer);
 }
 
 void
 Test_RtlFindNextForwardRunClear(void)
 {
     RTL_BITMAP BitMapHeader;
-    ULONG Buffer[2];
+    ULONG *Buffer;
     ULONG Index;
 
+    Buffer = AllocateGuarded(2 * sizeof(*Buffer));
     Buffer[0] = 0xF9F078B2;
     Buffer[1] = 0x3F303F30;
 
@@ -477,6 +583,7 @@ Test_RtlFindNextForwardRunClear(void)
     ok_int(Index, 17);
     ok_int(RtlFindNextForwardRunClear(&BitMapHeader, 39, &Index), 0);
     ok_int(Index, 39);
+    FreeGuarded(Buffer);
 }
 
 void