diff --git a/Include/internal/pycore_condvar.h b/Include/internal/pycore_condvar.h
index ee9533484e8048..55271f0a4116ba 100644
--- a/Include/internal/pycore_condvar.h
+++ b/Include/internal/pycore_condvar.h
@@ -31,7 +31,9 @@
 #define Py_HAVE_CONDVAR
 
 /* include windows if it hasn't been done before */
-#define WIN32_LEAN_AND_MEAN
+#ifndef WIN32_LEAN_AND_MEAN
+#  define WIN32_LEAN_AND_MEAN
+#endif
 #include <windows.h>              // CRITICAL_SECTION
 
 /* options */
diff --git a/Include/internal/pycore_semaphore.h b/Include/internal/pycore_semaphore.h
index ffcc6d80344d6e..269538384606ce 100644
--- a/Include/internal/pycore_semaphore.h
+++ b/Include/internal/pycore_semaphore.h
@@ -10,7 +10,9 @@
 #include "pycore_pythread.h"      // _POSIX_SEMAPHORES
 
 #ifdef MS_WINDOWS
-#   define WIN32_LEAN_AND_MEAN
+#   ifndef WIN32_LEAN_AND_MEAN
+#       define WIN32_LEAN_AND_MEAN
+#   endif
 #   include <windows.h>
 #elif defined(HAVE_PTHREAD_H)
 #   include <pthread.h>
diff --git a/Modules/_interpchannelsmodule.c b/Modules/_interpchannelsmodule.c
index fc54277cdc0ba0..ae64037d56cac0 100644
--- a/Modules/_interpchannelsmodule.c
+++ b/Modules/_interpchannelsmodule.c
@@ -11,7 +11,9 @@
 #include "pycore_pystate.h"       // _PyInterpreterState_GetIDObject()
 
 #ifdef MS_WINDOWS
-#define WIN32_LEAN_AND_MEAN
+#ifndef WIN32_LEAN_AND_MEAN
+#  define WIN32_LEAN_AND_MEAN
+#endif
 #include <windows.h>        // SwitchToThread()
 #elif defined(HAVE_SCHED_H)
 #include <sched.h>          // sched_yield()
diff --git a/Modules/_io/winconsoleio.c b/Modules/_io/winconsoleio.c
index 27c320ed073103..3f137fa1f54125 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/lock.c b/Python/lock.c
index 554c51d7780322..f2067ee2cd5f37 100644
--- a/Python/lock.c
+++ b/Python/lock.c
@@ -8,7 +8,9 @@
 #include "pycore_time.h"          // _PyTime_Add()
 
 #ifdef MS_WINDOWS
-#  define WIN32_LEAN_AND_MEAN
+#  ifndef WIN32_LEAN_AND_MEAN
+#    define WIN32_LEAN_AND_MEAN
+#  endif
 #  include <windows.h>            // SwitchToThread()
 #elif defined(HAVE_SCHED_H)
 #  include <sched.h>              // sched_yield()
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 8030bbbdeafd52..adaa5ee1c74aa5 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -45,7 +45,9 @@ Data members:
 #endif
 
 #ifdef MS_WINDOWS
-#  define WIN32_LEAN_AND_MEAN
+#  ifndef WIN32_LEAN_AND_MEAN
+#    define WIN32_LEAN_AND_MEAN
+#  endif
 #  include <windows.h>
 #endif /* MS_WINDOWS */