diff --git a/reactos/dll/win32/kernel32/client/fiber.c b/reactos/dll/win32/kernel32/client/fiber.c
index 338c9b7f9e5..2f7b901d50d 100644
--- a/reactos/dll/win32/kernel32/client/fiber.c
+++ b/reactos/dll/win32/kernel32/client/fiber.c
@@ -15,15 +15,15 @@
 typedef struct _FIBER                                      /* Field offsets:  */
 {                                                          /* 32 bit   64 bit */
     /* this must be the first field */
-    LPVOID Parameter;                                      /*   0x00     0x00 */
-    struct _EXCEPTION_REGISTRATION_RECORD * ExceptionList; /*   0x04     0x08 */
-    LPVOID StackBase;                                      /*   0x08     0x10 */
-    LPVOID StackLimit;                                     /*   0x0C     0x18 */
-    LPVOID DeallocationStack;                              /*   0x10     0x20 */
+    PVOID Parameter;                                       /*   0x00     0x00 */
+    PEXCEPTION_REGISTRATION_RECORD ExceptionList;          /*   0x04     0x08 */
+    PVOID StackBase;                                       /*   0x08     0x10 */
+    PVOID StackLimit;                                      /*   0x0C     0x18 */
+    PVOID DeallocationStack;                               /*   0x10     0x20 */
     CONTEXT Context;                                       /*   0x14     0x28 */
     ULONG GuaranteedStackBytes;                            /*   0x2E0         */
     PVOID FlsData;                                         /*   0x2E4         */
-    PVOID ActivationContextStack;                          /*   0x2E8         */
+    PACTIVATION_CONTEXT_STACK ActivationContextStack;      /*   0x2E8         */
 } FIBER, *PFIBER;
 
 /* PRIVATE FUNCTIONS **********************************************************/
@@ -171,7 +171,7 @@ CreateFiberEx(SIZE_T dwStackCommitSize,
     PFIBER Fiber;
     NTSTATUS Status;
     INITIAL_TEB InitialTeb;
-    PVOID ActivationContextStack = NULL;
+    PACTIVATION_CONTEXT_STACK ActivationContextStack = NULL;
     DPRINT("Creating Fiber\n");
 
     /* Check for invalid flags */
@@ -210,9 +210,8 @@ CreateFiberEx(SIZE_T dwStackCommitSize,
         /* Free the fiber */
         RtlFreeHeap(GetProcessHeap(), 0, Fiber);
 
-        /* Free the activation context */
-        DPRINT1("Leaking activation stack because nobody implemented free");
-        //RtlFreeActivationContextStack(&ActivationContextStack);
+        /* Free the activation context stack */
+        RtlFreeActivationContextStack(ActivationContextStack);
 
         /* Failure */
         BaseSetLastNTError(Status);
@@ -271,9 +270,8 @@ DeleteFiber(LPVOID lpFiber)
     /* Get rid of FLS */
     if (Fiber->FlsData) BaseRundownFls(Fiber->FlsData);
 
-    /* Get rid of the activation stack */
-    DPRINT1("Leaking activation stack because nobody implemented free");
-    //RtlFreeActivationContextStack(Fiber->ActivationContextStack);
+    /* Get rid of the activation context stack */
+    RtlFreeActivationContextStack(Fiber->ActivationContextStack);
 
     /* Free the fiber data */
     RtlFreeHeap(GetProcessHeap(), 0, lpFiber);
diff --git a/reactos/dll/win32/kernel32/client/thread.c b/reactos/dll/win32/kernel32/client/thread.c
index 56da4337949..504c0356b2b 100644
--- a/reactos/dll/win32/kernel32/client/thread.c
+++ b/reactos/dll/win32/kernel32/client/thread.c
@@ -171,7 +171,7 @@ CreateRemoteThread(IN HANDLE hProcess,
     ULONG Dummy;
     PTEB Teb;
     THREAD_BASIC_INFORMATION ThreadBasicInfo;
-    PVOID ActivationContextStack = NULL;
+    PACTIVATION_CONTEXT_STACK ActivationContextStack = NULL;
     ACTIVATION_CONTEXT_BASIC_INFORMATION ActCtxInfo;
     ULONG_PTR Cookie;
     ULONG ReturnLength;
@@ -191,7 +191,7 @@ CreateRemoteThread(IN HANDLE hProcess,
                              dwCreationFlags & STACK_SIZE_PARAM_IS_A_RESERVATION ?
                              dwStackSize : 0,
                              &InitialTeb);
-    if(!NT_SUCCESS(Status))
+    if (!NT_SUCCESS(Status))
     {
         BaseSetLastNTError(Status);
         return NULL;
@@ -260,7 +260,7 @@ CreateRemoteThread(IN HANDLE hProcess,
         Teb->ActivationContextStackPointer = ActivationContextStack;
 
         /* Query the Context */
-         // WARNING!!! THIS IS USING THE WIN32 FLAG BECAUSE REACTOS CONTINUES TO BE A POS!!! ///
+        // WARNING!!! THIS IS USING THE WIN32 FLAG BECAUSE REACTOS CONTINUES TO BE A POS!!! ///
         Status = RtlQueryInformationActivationContext(QUERY_ACTCTX_FLAG_USE_ACTIVE_ACTCTX,
                                                       NULL,
                                                       0,
@@ -274,6 +274,11 @@ CreateRemoteThread(IN HANDLE hProcess,
             ERROR_DBGBREAK("SXS: %s - Failing thread create because "
                            "RtlQueryInformationActivationContext() failed with status %08lx\n",
                            __FUNCTION__, Status);
+
+            /* Free the activation context stack */
+            // RtlFreeThreadActivationContextStack();
+            RtlFreeActivationContextStack(Teb->ActivationContextStackPointer);
+
             return NULL;
         }
 
@@ -291,6 +296,11 @@ CreateRemoteThread(IN HANDLE hProcess,
                 ERROR_DBGBREAK("SXS: %s - Failing thread create because "
                                "RtlActivateActivationContextEx() failed with status %08lx\n",
                                __FUNCTION__, Status);
+
+                /* Free the activation context stack */
+                // RtlFreeThreadActivationContextStack();
+                RtlFreeActivationContextStack(Teb->ActivationContextStackPointer);
+
                 return NULL;
             }
         }
@@ -299,7 +309,6 @@ CreateRemoteThread(IN HANDLE hProcess,
     /* Notify CSR */
     if (!BaseRunningInServerProcess)
     {
-        /* Notify CSR */
         Status = BasepNotifyCsrOfThread(hThread, &ClientId);
         ASSERT(NT_SUCCESS(Status));
     }