diff --git a/dll/win32/kernel32/CMakeLists.txt b/dll/win32/kernel32/CMakeLists.txt
index 7d31686837d..4f4eddc4f8f 100644
--- a/dll/win32/kernel32/CMakeLists.txt
+++ b/dll/win32/kernel32/CMakeLists.txt
@@ -99,8 +99,7 @@ if(ARCH STREQUAL "i386")
         client/i386/thread.S)
 elseif(ARCH STREQUAL "amd64")
     list(APPEND ASM_SOURCE
-        client/amd64/fiber.S
-        client/amd64/thread.S)
+        client/amd64/fiber.S)
 elseif(ARCH STREQUAL "arm")
     list(APPEND ASM_SOURCE
         client/arm/fiber.S
diff --git a/dll/win32/kernel32/client/amd64/thread.S b/dll/win32/kernel32/client/amd64/thread.S
deleted file mode 100644
index 575789ef17f..00000000000
--- a/dll/win32/kernel32/client/amd64/thread.S
+++ /dev/null
@@ -1,38 +0,0 @@
-/*
- * COPYRIGHT:  See COPYING in the top level directory
- * PROJECT:    ReactOS system libraries
- * FILE:       dll/win32/kernel32/client/amd64/thread.S
- * PURPOSE:    Thread Start Thunks
- * PROGRAMMER: Alex Ionescu (alex@relsoft.net)
- */
-
-#include <asm.inc>
-.code64
-
-EXTERN BaseThreadStartup:PROC
-EXTERN BaseProcessStartup:PROC
-
-PUBLIC BaseThreadStartupThunk
-PUBLIC BaseProcessStartThunk
-
-BaseThreadStartupThunk:
-
-    /* Start out fresh */
-    xor rbp, rbp
-
-    push rbx                  /* lpParameter */
-    push rax                  /* lpStartAddress */
-    push 0                    /* Return RIP */
-    jmp BaseThreadStartup
-
-BaseProcessStartThunk:
-
-    /* Start out fresh */
-    xor rbp, rbp
-
-    push rax                  /* lpStartAddress */
-    push 0                    /* Return RIP */
-    jmp BaseProcessStartup
-
-END
-/* EOF */
diff --git a/dll/win32/kernel32/client/utils.c b/dll/win32/kernel32/client/utils.c
index 6e3a3368ad5..c10d2d45004 100644
--- a/dll/win32/kernel32/client/utils.c
+++ b/dll/win32/kernel32/client/utils.c
@@ -580,12 +580,14 @@ BaseInitializeContext(IN PCONTEXT Context,
 
 #elif defined(_M_AMD64)
     DPRINT("BaseInitializeContext: %p\n", Context);
+    ASSERT(((ULONG_PTR)StackAddress & 15) == 0);
+
+    RtlZeroMemory(Context, sizeof(*Context));
 
     /* Setup the Initial Win32 Thread Context */
-    Context->Rax = (ULONG_PTR)StartAddress;
-    Context->Rbx = (ULONG_PTR)Parameter;
-    Context->Rsp = (ULONG_PTR)StackAddress;
-    /* The other registers are undefined */
+    Context->Rcx = (ULONG_PTR)StartAddress;
+    Context->Rdx = (ULONG_PTR)Parameter;
+    Context->Rsp = (ULONG_PTR)StackAddress - 5 * sizeof(PVOID);
 
     /* Setup the Segments */
     Context->SegGs = KGDT64_R3_DATA | RPL_MASK;
@@ -596,11 +598,11 @@ BaseInitializeContext(IN PCONTEXT Context,
     Context->SegFs = KGDT64_R3_CMTEB | RPL_MASK;
 
     /* Set the EFLAGS */
-    Context->EFlags = 0x3000; /* IOPL 3 */
+    Context->EFlags = 0x3000 | EFLAGS_INTERRUPT_MASK; /* IOPL 3 */
 
     if (ContextType == 1)      /* For Threads */
     {
-        Context->Rip = (ULONG_PTR)BaseThreadStartupThunk;
+        Context->Rip = (ULONG_PTR)BaseThreadStartup;
     }
     else if (ContextType == 2) /* For Fibers */
     {
@@ -608,14 +610,11 @@ BaseInitializeContext(IN PCONTEXT Context,
     }
     else                       /* For first thread in a Process */
     {
-        Context->Rip = (ULONG_PTR)BaseProcessStartThunk;
+        Context->Rip = (ULONG_PTR)BaseProcessStartup;
     }
 
     /* Set the Context Flags */
     Context->ContextFlags = CONTEXT_FULL;
-
-    /* Give it some room for the Parameter */
-    Context->Rsp -= sizeof(PVOID);
 #elif defined(_M_ARM)
     DPRINT("BaseInitializeContext: %p\n", Context);