diff --git a/reactos/include/reactos/win32k/ntuser.h b/reactos/include/reactos/win32k/ntuser.h
index cd4e2977478..3a5840fbceb 100644
--- a/reactos/include/reactos/win32k/ntuser.h
+++ b/reactos/include/reactos/win32k/ntuser.h
@@ -2243,7 +2243,7 @@ NtUserSetSysColors(
   int cElements,
   IN CONST INT *lpaElements,
   IN CONST COLORREF *lpaRgbValues,
-  DWORD Unknown3);
+  FLONG Flags);
 
 BOOL
 NTAPI
diff --git a/reactos/subsystems/win32/win32k/ntuser/ntstubs.c b/reactos/subsystems/win32/win32k/ntuser/ntstubs.c
index 79ed471a003..2d3a9744c18 100644
--- a/reactos/subsystems/win32/win32k/ntuser/ntstubs.c
+++ b/reactos/subsystems/win32/win32k/ntuser/ntstubs.c
@@ -527,7 +527,7 @@ NtUserSetSysColors(
    int cElements,
    IN CONST INT *lpaElements,
    IN CONST COLORREF *lpaRgbValues,
-   DWORD Unknown3)
+   FLONG Flags)
 {
   DWORD Ret = FALSE;
   NTSTATUS Status = STATUS_SUCCESS;