diff --git a/base/system/smss/smsbapi.c b/base/system/smss/smsbapi.c
index e1b21f7bdb3..f8eafe45a3f 100644
--- a/base/system/smss/smsbapi.c
+++ b/base/system/smss/smsbapi.c
@@ -36,28 +36,28 @@ NTAPI
 SmpSbCreateSession(IN PVOID Reserved,
                    IN PSMP_SUBSYSTEM OtherSubsystem,
                    IN PRTL_USER_PROCESS_INFORMATION ProcessInformation,
-                   IN ULONG MuSessionId,
-                   IN PCLIENT_ID DbgClientId)
+                   IN ULONG DbgSessionId,
+                   IN PCLIENT_ID DbgUiClientId)
 {
     NTSTATUS Status;
     ULONG SubSystemType = ProcessInformation->ImageInformation.SubSystemType;
-    PSMP_SUBSYSTEM KnownSubsys;
-    SB_API_MSG SbApiMsg;
+    ULONG MuSessionId;
     ULONG SessionId;
-    PSB_CREATE_SESSION_MSG CreateSessionMsg;
+    PSMP_SUBSYSTEM KnownSubsys;
+    SB_API_MSG SbApiMsg = {0};
+    PSB_CREATE_SESSION_MSG CreateSessionMsg = &SbApiMsg.u.CreateSession;
 
     /* Write out the create session message including its initial process */
-    CreateSessionMsg = &SbApiMsg.u.CreateSession;
     CreateSessionMsg->ProcessInfo = *ProcessInformation;
-    CreateSessionMsg->MuSessionId = MuSessionId;
-    if (DbgClientId)
+    CreateSessionMsg->DbgSessionId = DbgSessionId;
+    if (DbgUiClientId)
     {
-        CreateSessionMsg->ClientId = *DbgClientId;
+        CreateSessionMsg->DbgUiClientId = *DbgUiClientId;
     }
     else
     {
-        CreateSessionMsg->ClientId.UniqueThread = NULL;
-        CreateSessionMsg->ClientId.UniqueProcess = NULL;
+        CreateSessionMsg->DbgUiClientId.UniqueThread = NULL;
+        CreateSessionMsg->DbgUiClientId.UniqueProcess = NULL;
     }
 
     /* Find a subsystem responsible for this session */
@@ -70,7 +70,7 @@ SmpSbCreateSession(IN PVOID Reserved,
         return STATUS_OBJECT_NAME_NOT_FOUND;
     }
 
-    /* Find the subsystem we have for this initial process */
+    /* Find the subsystem suitable for this initial process */
     KnownSubsys = SmpLocateKnownSubSysByType(MuSessionId, SubSystemType);
     if (KnownSubsys)
     {
@@ -169,8 +169,13 @@ SmpSbCreateSession(IN PVOID Reserved,
     }
 
 #if 0
-    /* This code handles debug applications, but it seems vestigial... */
-    if ((*(ULONGLONG)&CreateSessionMsg.ClientId) && (SmpDbgSsLoaded))
+    /*
+     * This code is part of the LPC-based legacy debugging support for native
+     * applications, implemented with the debug client interface (DbgUi) and
+     * debug subsystem (DbgSs). It is now vestigial since WinXP+ and is here
+     * for informational purposes only.
+     */
+    if ((*(ULONGLONG)&CreateSessionMsg.DbgUiClientId) && SmpDbgSsLoaded)
     {
         Process = RtlAllocateHeap(SmpHeap, SmBaseTag, sizeof(SMP_PROCESS));
         if (!Process)
@@ -183,12 +188,17 @@ SmpSbCreateSession(IN PVOID Reserved,
             return STATUS_NO_MEMORY;
         }
 
-        Process->DbgClientId = CreateSessionMsg->ClientId;
+        Process->DbgUiClientId = CreateSessionMsg->DbgUiClientId;
         Process->ClientId = ProcessInformation->ClientId;
         InsertHeadList(&NativeProcessList, &Process->Entry);
-        DPRINT1("Native Debug App %lx.%lx\n", Process->ClientId.UniqueProcess, Process->ClientId.UniqueThread);
+        DPRINT1("Native Debug App %lx.%lx\n",
+                Process->ClientId.UniqueProcess,
+                Process->ClientId.UniqueThread);
 
-        Status = NtSetInformationProcess(ProcessInformation->ProcessHandle, 7, &SmpDebugPort, 4);
+        Status = NtSetInformationProcess(ProcessInformation->ProcessHandle,
+                                         ProcessDebugPort,
+                                         &SmpDebugPort,
+                                         sizeof(SmpDebugPort));
         ASSERT(NT_SUCCESS(Status));
     }
 #endif
diff --git a/base/system/smss/smss.h b/base/system/smss/smss.h
index fb63117cea5..4798f570d2f 100644
--- a/base/system/smss/smss.h
+++ b/base/system/smss/smss.h
@@ -168,8 +168,8 @@ SmpSbCreateSession(
     IN PVOID Reserved,
     IN PSMP_SUBSYSTEM OtherSubsystem,
     IN PRTL_USER_PROCESS_INFORMATION ProcessInformation,
-    IN ULONG MuSessionId,
-    IN PCLIENT_ID DbgClientId
+    IN ULONG DbgSessionId,
+    IN PCLIENT_ID DbgUiClientId
 );
 
 /* smsessn.c */
diff --git a/base/system/smss/smsubsys.c b/base/system/smss/smsubsys.c
index 1d6738c8237..40bcfa946f6 100644
--- a/base/system/smss/smsubsys.c
+++ b/base/system/smss/smsubsys.c
@@ -145,7 +145,7 @@ SmpLoadSubSystem(IN PUNICODE_STRING FileName,
     PSMP_SUBSYSTEM Subsystem, NewSubsystem, KnownSubsystem = NULL;
     HANDLE SubSysProcessId;
     NTSTATUS Status = STATUS_SUCCESS;
-    SB_API_MSG SbApiMsg, SbApiMsg2;
+    SB_API_MSG SbApiMsg;
     RTL_USER_PROCESS_INFORMATION ProcessInformation;
     LARGE_INTEGER Timeout;
     PVOID State;
@@ -316,13 +316,10 @@ SmpLoadSubSystem(IN PUNICODE_STRING FileName,
     else
     {
         /* This is the POSIX or OS/2 subsystem process, copy its information */
-        RtlCopyMemory(&CreateSession->ProcessInfo,
-                      &ProcessInformation,
-                      sizeof(CreateSession->ProcessInfo));
+        CreateSession->ProcessInfo = ProcessInformation;
 
-        /* Not sure these field mean what I think they do -- but clear them */
-        *(PULONGLONG)&CreateSession->ClientId = 0;
-        CreateSession->MuSessionId = 0;
+        CreateSession->DbgSessionId = 0;
+        *(PULONGLONG)&CreateSession->DbgUiClientId = 0;
 
         /* This should find CSRSS because they are POSIX or OS/2 subsystems */
         Subsystem = SmpLocateKnownSubSysByType(MuSessionId,
@@ -372,25 +369,25 @@ SmpLoadSubSystem(IN PUNICODE_STRING FileName,
         }
 
         /* Allocate an internal Session ID for this subsystem */
-        MuSessionId = SmpAllocateSessionId(Subsystem, 0);
-        CreateSession->SessionId = MuSessionId;
+        CreateSession->SessionId = SmpAllocateSessionId(Subsystem, NULL);
 
         /* Send the create session message to the subsystem */
-        SbApiMsg2.ReturnValue = STATUS_SUCCESS;
-        SbApiMsg2.h.u2.ZeroInit = 0;
-        SbApiMsg2.h.u1.s1.DataLength = sizeof(SB_CREATE_SESSION_MSG) + 8;
-        SbApiMsg2.h.u1.s1.TotalLength = sizeof(SB_API_MSG);
+        SbApiMsg.ReturnValue = STATUS_SUCCESS;
+        SbApiMsg.h.u2.ZeroInit = 0;
+        SbApiMsg.h.u1.s1.DataLength = sizeof(SB_CREATE_SESSION_MSG) + 8;
+        SbApiMsg.h.u1.s1.TotalLength = sizeof(SB_API_MSG);
+        SbApiMsg.ApiNumber = SbpCreateSession;
         Status = NtRequestWaitReplyPort(Subsystem->SbApiPort,
-                                        &SbApiMsg2.h,
-                                        &SbApiMsg2.h);
-        if (NT_SUCCESS(Status)) Status = SbApiMsg2.ReturnValue;
+                                        &SbApiMsg.h,
+                                        &SbApiMsg.h);
+        if (NT_SUCCESS(Status)) Status = SbApiMsg.ReturnValue;
         if (!NT_SUCCESS(Status))
         {
             /* Delete the session and handle failure if the LPC call failed */
             SmpDeleteSession(CreateSession->SessionId);
             DPRINT1("SMSS: SmpLoadSubSystem - NtRequestWaitReplyPort Failed with  Status %lx for sessionid %lu\n",
                     Status,
-                    CreateSession->SessionId);
+                    MuSessionId);
             goto Quickie;
         }
     }
diff --git a/sdk/include/reactos/subsys/sm/smmsg.h b/sdk/include/reactos/subsys/sm/smmsg.h
index ada3ae670bc..50601e38409 100644
--- a/sdk/include/reactos/subsys/sm/smmsg.h
+++ b/sdk/include/reactos/subsys/sm/smmsg.h
@@ -159,9 +159,9 @@ typedef struct _SB_CREATE_SESSION_MSG
 {
     ULONG SessionId;
     RTL_USER_PROCESS_INFORMATION ProcessInfo;
-    PVOID Unknown;
-    ULONG MuSessionId;
-    CLIENT_ID ClientId;
+    PVOID Reserved;
+    ULONG DbgSessionId;
+    CLIENT_ID DbgUiClientId;
 } SB_CREATE_SESSION_MSG, *PSB_CREATE_SESSION_MSG;
 #ifndef _WIN64
 C_ASSERT(sizeof(SB_CREATE_SESSION_MSG) == 0x58);