diff --git a/ntoskrnl/ke/amd64/thrdini.c b/ntoskrnl/ke/amd64/thrdini.c
index e6518e0bf82..8a2f206915e 100644
--- a/ntoskrnl/ke/amd64/thrdini.c
+++ b/ntoskrnl/ke/amd64/thrdini.c
@@ -46,6 +46,7 @@ KiInitializeContextThread(IN PKTHREAD Thread,
     PKSTART_FRAME StartFrame;
     PKSWITCH_FRAME CtxSwitchFrame;
     PKTRAP_FRAME TrapFrame;
+    PKEXCEPTION_FRAME ExceptionFrame;
     ULONG ContextFlags;
     PVOID InitialStack;
 
@@ -102,19 +103,37 @@ KiInitializeContextThread(IN PKTHREAD Thread,
         ASSERT((Context->ContextFlags & CONTEXT_CONTROL) == CONTEXT_CONTROL);
         ContextFlags = Context->ContextFlags & ~CONTEXT_DEBUG_REGISTERS;
 
-        /* Setup the Trap Frame */
+        /* Zero-initialize the Trap Frame and exception frame */
         TrapFrame = &InitFrame->TrapFrame;
-
-        /* Zero out the trap frame */
         RtlZeroMemory(TrapFrame, sizeof(KTRAP_FRAME));
-        RtlZeroMemory(&InitFrame->ExceptionFrame, sizeof(KEXCEPTION_FRAME));
+        ExceptionFrame = &InitFrame->ExceptionFrame;
+        RtlZeroMemory(ExceptionFrame, sizeof(KEXCEPTION_FRAME));
 
-        /* Set up a trap frame from the context. */
-        KeContextToTrapFrame(Context,
-                             &InitFrame->ExceptionFrame,
-                             TrapFrame,
-                             CONTEXT_AMD64 | ContextFlags,
-                             UserMode);
+        /* Copy integer registers */
+        TrapFrame->Rax = Context->Rax;
+        TrapFrame->Rcx = Context->Rcx;
+        TrapFrame->Rdx = Context->Rdx;
+        TrapFrame->Rbp = 0; // Context->Rbp; // 0 on Vista, copied on Win 10
+        TrapFrame->R8 = Context->R8;
+        TrapFrame->R9 = Context->R9;
+        TrapFrame->R10 = Context->R10;
+        TrapFrame->R11 = Context->R11;
+        ExceptionFrame->Rbx = Context->Rbx;
+        ExceptionFrame->Rsi = Context->Rsi;
+        ExceptionFrame->Rdi = Context->Rdi;
+        ExceptionFrame->R12 = Context->R12;
+        ExceptionFrame->R13 = Context->R13;
+        ExceptionFrame->R14 = Context->R14;
+        ExceptionFrame->R15 = Context->R15;
+
+        /* Copy RIP, RSP, EFLAGS */
+        TrapFrame->Rip = Context->Rip;
+        TrapFrame->Rsp = Context->Rsp;
+        TrapFrame->EFlags = Context->EFlags;
+
+        /* Sanitize EFLAGS */
+        TrapFrame->EFlags &= EFLAGS_USER_THREAD_SANITIZE;
+        TrapFrame->EFlags |= EFLAGS_INTERRUPT_MASK;
 
         /* Set user mode segment selectors */
         TrapFrame->SegDs = KGDT64_R3_DATA | RPL_MASK;
@@ -127,6 +146,9 @@ KiInitializeContextThread(IN PKTHREAD Thread,
         /* Clear DR7 */
         TrapFrame->Dr7 = 0;
 
+        /* Initialize floating point state */
+        TrapFrame->MxCsr = INITIAL_MXCSR;
+
         /* Set the previous mode as user */
         TrapFrame->PreviousMode = UserMode;
 
@@ -137,7 +159,7 @@ KiInitializeContextThread(IN PKTHREAD Thread,
         StartFrame->Return = (ULONG64)KiUserThreadStartupExit;
 
         /* KiUserThreadStartupExit returns to KiServiceExit3 */
-        InitFrame->ExceptionFrame.Return = (ULONG64)KiServiceExit3;
+        ExceptionFrame->Return = (ULONG64)KiServiceExit3;
 
         /* Allocate home space on the stack */
         TrapFrame->Rsp -= 5 * sizeof(PVOID);
diff --git a/sdk/include/ndk/amd64/ketypes.h b/sdk/include/ndk/amd64/ketypes.h
index e23d0c7d1b0..0064a9ca8ec 100644
--- a/sdk/include/ndk/amd64/ketypes.h
+++ b/sdk/include/ndk/amd64/ketypes.h
@@ -191,10 +191,15 @@ typedef enum
 // EFlags
 //
 #define EFLAGS_CF               0x01L
+#define EFLAGS_RESERVED1        0x02L
+#define EFLAGS_PF               0x04L
+#define EFLAGS_AF               0x10L
 #define EFLAGS_ZF               0x40L
+#define EFLAGS_SF               0x80L
 #define EFLAGS_TF               0x100L
 #define EFLAGS_INTERRUPT_MASK   0x200L
 #define EFLAGS_DF               0x400L
+#define EFLAGS_OF               0x800L
 #define EFLAGS_IOPL             0x3000L
 #define EFLAGS_NESTED_TASK      0x4000L
 //#define EFLAGS_NF               0x4000
@@ -212,6 +217,7 @@ typedef enum
 #define EFLAGS_ID_MASK          0x200000
 #define EFLAGS_IF_MASK          0x0200
 #define EFLAGS_IF_SHIFT         0x0009
+#define EFLAGS_USER_THREAD_SANITIZE 0x200FD5 /* Allowed flags: ID|OF|DF|IF|TF|SF|ZF|AF|PF|CF */
 
 //
 // MXCSR Floating Control/Status Bit Masks