diff --git a/mongoose.h b/mongoose.h
index 54fd3fdb..3f6cb64e 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -48,10 +48,6 @@ extern "C" {
 #endif
 #endif  // !defined(MG_ARCH)
 
-#define WIN32_LEAN_AND_MEAN
-#define _CRT_SECURE_NO_WARNINGS
-#define _WINSOCK_DEPRECATED_NO_WARNINGS
-
 #if !defined(PRINTF_LIKE)
 #if defined(__GNUC__) || defined(__clang__) || defined(__TI_COMPILER_VERSION__)
 #define PRINTF_LIKE(f, a) __attribute__((format(printf, f, a)))
@@ -296,6 +292,18 @@ struct timeval {
 
 #if MG_ARCH == MG_ARCH_WIN32
 
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+
+#ifndef _CRT_SECURE_NO_WARNINGS
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+
+#ifndef _WINSOCK_DEPRECATED_NO_WARNINGS
+#define _WINSOCK_DEPRECATED_NO_WARNINGS
+#endif
+
 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
diff --git a/src/arch.h b/src/arch.h
index da10088a..21339519 100644
--- a/src/arch.h
+++ b/src/arch.h
@@ -26,10 +26,6 @@
 #endif
 #endif  // !defined(MG_ARCH)
 
-#define WIN32_LEAN_AND_MEAN
-#define _CRT_SECURE_NO_WARNINGS
-#define _WINSOCK_DEPRECATED_NO_WARNINGS
-
 #if !defined(PRINTF_LIKE)
 #if defined(__GNUC__) || defined(__clang__) || defined(__TI_COMPILER_VERSION__)
 #define PRINTF_LIKE(f, a) __attribute__((format(printf, f, a)))
diff --git a/src/arch_win32.h b/src/arch_win32.h
index b0e6166d..a95c1119 100644
--- a/src/arch_win32.h
+++ b/src/arch_win32.h
@@ -2,6 +2,18 @@
 
 #if MG_ARCH == MG_ARCH_WIN32
 
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+
+#ifndef _CRT_SECURE_NO_WARNINGS
+#define _CRT_SECURE_NO_WARNINGS
+#endif
+
+#ifndef _WINSOCK_DEPRECATED_NO_WARNINGS
+#define _WINSOCK_DEPRECATED_NO_WARNINGS
+#endif
+
 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>