diff --git a/Include/internal/pycore_condvar.h b/Include/internal/pycore_condvar.h
index 981c962bf7dfdf..2177bed31fcd27 100644
--- a/Include/internal/pycore_condvar.h
+++ b/Include/internal/pycore_condvar.h
@@ -37,8 +37,10 @@
 #define Py_HAVE_CONDVAR
 
 /* include windows if it hasn't been done before */
-#define WIN32_LEAN_AND_MEAN
-#include <windows.h>
+#ifndef WIN32_LEAN_AND_MEAN
+#  define WIN32_LEAN_AND_MEAN
+#endif
+#include <windows.h>              // CRITICAL_SECTION
 
 /* options */
 /* non-emulated condition variables are provided for those that want
diff --git a/Modules/_io/winconsoleio.c b/Modules/_io/winconsoleio.c
index da4907ec2db2a8..164789ef218524 100644
--- a/Modules/_io/winconsoleio.c
+++ b/Modules/_io/winconsoleio.c
@@ -23,7 +23,7 @@
 #include <stddef.h> /* For offsetof */
 
 #ifndef WIN32_LEAN_AND_MEAN
-#define WIN32_LEAN_AND_MEAN
+#  define WIN32_LEAN_AND_MEAN
 #endif
 #include <windows.h>
 #include <fcntl.h>
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index e3bdff15a856bf..6ed28ec5fbd8ba 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -39,8 +39,10 @@ Data members:
 #include <locale.h>
 
 #ifdef MS_WINDOWS
-#define WIN32_LEAN_AND_MEAN
-#include <windows.h>
+#  ifndef WIN32_LEAN_AND_MEAN
+#    define WIN32_LEAN_AND_MEAN
+#  endif
+#  include <windows.h>
 #endif /* MS_WINDOWS */
 
 #ifdef MS_COREDLL