diff --git a/winpr/include/winpr/synch.h b/winpr/include/winpr/synch.h
index 28d15fa23..ddefaa95a 100644
--- a/winpr/include/winpr/synch.h
+++ b/winpr/include/winpr/synch.h
@@ -271,7 +271,7 @@ WINPR_API BOOL CancelWaitableTimer(HANDLE hTimer);
 
 #endif
 
-#if ((_WIN32) && (_WIN32_WINNT < 0x0600))
+#if ((_WIN32) && (_WIN32_WINNT < 0x0403))
 
 WINPR_API BOOL InitializeCriticalSectionEx(LPCRITICAL_SECTION lpCriticalSection, DWORD dwSpinCount, DWORD Flags);
 
diff --git a/winpr/libwinpr/synch/critical.c b/winpr/libwinpr/synch/critical.c
index 90909e67f..6f7ecdf9e 100644
--- a/winpr/libwinpr/synch/critical.c
+++ b/winpr/libwinpr/synch/critical.c
@@ -235,7 +235,7 @@ VOID DeleteCriticalSection(LPCRITICAL_SECTION lpCriticalSection)
 
 #endif
 
-#if ((_WIN32) && (_WIN32_WINNT < 0x0600))
+#if ((_WIN32) && (_WIN32_WINNT < 0x0403))
 
 typedef BOOL (WINAPI * PINITIALIZE_CRITICAL_SECTION_EX_FN)(LPCRITICAL_SECTION lpCriticalSection, DWORD dwSpinCount, DWORD Flags);