diff --git a/dlls/api-ms-win-core-processthreads-l1-1-1/api-ms-win-core-processthreads-l1-1-1.spec b/dlls/api-ms-win-core-processthreads-l1-1-1/api-ms-win-core-processthreads-l1-1-1.spec
index e4cfec2b645..c0187f100fe 100644
--- a/dlls/api-ms-win-core-processthreads-l1-1-1/api-ms-win-core-processthreads-l1-1-1.spec
+++ b/dlls/api-ms-win-core-processthreads-l1-1-1/api-ms-win-core-processthreads-l1-1-1.spec
@@ -28,7 +28,7 @@
 @ stdcall GetStartupInfoW(ptr) kernel32.GetStartupInfoW
 @ stdcall GetThreadContext(long ptr) kernel32.GetThreadContext
 @ stdcall GetThreadId(ptr) kernel32.GetThreadId
-@ stub GetThreadIdealProcessorEx
+@ stdcall GetThreadIdealProcessorEx(long ptr) kernel32.GetThreadIdealProcessorEx
 @ stdcall GetThreadPriority(long) kernel32.GetThreadPriority
 @ stdcall GetThreadPriorityBoost(long ptr) kernel32.GetThreadPriorityBoost
 @ stdcall GetThreadTimes(long ptr ptr ptr ptr) kernel32.GetThreadTimes
diff --git a/dlls/api-ms-win-core-processthreads-l1-1-2/api-ms-win-core-processthreads-l1-1-2.spec b/dlls/api-ms-win-core-processthreads-l1-1-2/api-ms-win-core-processthreads-l1-1-2.spec
index 45d52ff1715..793015cf536 100644
--- a/dlls/api-ms-win-core-processthreads-l1-1-2/api-ms-win-core-processthreads-l1-1-2.spec
+++ b/dlls/api-ms-win-core-processthreads-l1-1-2/api-ms-win-core-processthreads-l1-1-2.spec
@@ -31,7 +31,7 @@
 @ stdcall GetThreadContext(long ptr) kernel32.GetThreadContext
 @ stdcall GetThreadIOPendingFlag(long ptr) kernel32.GetThreadIOPendingFlag
 @ stdcall GetThreadId(ptr) kernel32.GetThreadId
-@ stub GetThreadIdealProcessorEx
+@ stdcall GetThreadIdealProcessorEx(long ptr) kernel32.GetThreadIdealProcessorEx
 @ stub GetThreadInformation
 @ stdcall GetThreadPriority(long) kernel32.GetThreadPriority
 @ stdcall GetThreadPriorityBoost(long ptr) kernel32.GetThreadPriorityBoost
diff --git a/dlls/kernel32/kernel32.spec b/dlls/kernel32/kernel32.spec
index be48ef16948..f9295dc3ee4 100644
--- a/dlls/kernel32/kernel32.spec
+++ b/dlls/kernel32/kernel32.spec
@@ -853,7 +853,7 @@
 @ stdcall -import GetThreadGroupAffinity(long ptr)
 @ stdcall -import GetThreadIOPendingFlag(long ptr)
 @ stdcall -import GetThreadId(ptr)
-# @ stub GetThreadIdealProcessorEx
+@ stdcall -import GetThreadIdealProcessorEx(long ptr)
 @ stdcall -import GetThreadLocale()
 @ stdcall GetThreadPreferredUILanguages(long ptr ptr ptr)
 @ stdcall -import GetThreadPriority(long)
diff --git a/dlls/kernelbase/kernelbase.spec b/dlls/kernelbase/kernelbase.spec
index f36d4d525c9..caa6de1d516 100644
--- a/dlls/kernelbase/kernelbase.spec
+++ b/dlls/kernelbase/kernelbase.spec
@@ -716,7 +716,7 @@
 @ stdcall GetThreadGroupAffinity(long ptr)
 @ stdcall GetThreadIOPendingFlag(long ptr)
 @ stdcall GetThreadId(ptr)
-# @ stub GetThreadIdealProcessorEx
+@ stdcall GetThreadIdealProcessorEx(long ptr)
 # @ stub GetThreadInformation
 @ stdcall GetThreadLocale()
 @ stdcall GetThreadPreferredUILanguages(long ptr ptr ptr) kernel32.GetThreadPreferredUILanguages
diff --git a/dlls/kernelbase/thread.c b/dlls/kernelbase/thread.c
index f669c9d8734..6af9ffa4068 100644
--- a/dlls/kernelbase/thread.c
+++ b/dlls/kernelbase/thread.c
@@ -245,6 +245,17 @@ DWORD WINAPI DECLSPEC_HOTPATCH GetThreadId( HANDLE thread )
 }
 
 
+/***********************************************************************
+ *           GetThreadIdealProcessorEx   (kernelbase.@)
+ */
+BOOL WINAPI /* DECLSPEC_HOTPATCH */ GetThreadIdealProcessorEx( HANDLE thread, PROCESSOR_NUMBER *ideal )
+{
+    FIXME( "(%p %p): stub\n", thread, ideal );
+    SetLastError( ERROR_CALL_NOT_IMPLEMENTED );
+    return FALSE;
+}
+
+
 /***********************************************************************
  *	GetThreadLocale   (kernelbase.@)
  */