diff --git a/library/entropy_poll.c b/library/entropy_poll.c
index b5024c8..8b60ee5 100644
--- a/library/entropy_poll.c
+++ b/library/entropy_poll.c
@@ -52,6 +52,7 @@
 #define _WIN32_WINNT 0x0400
 #endif
 #include <windows.h>
+#if _WIN32_WINNT >= 0x0501 /* _WIN32_WINNT_WINXP */
 #include <wincrypt.h>
 
 int mbedtls_platform_entropy_poll(void *data, unsigned char *output, size_t len,
@@ -76,6 +77,9 @@
 
     return 0;
 }
+#else /* !_WIN32_WINNT_WINXP */
+#error Entropy not available before Windows XP, use MBEDTLS_NO_PLATFORM_ENTROPY
+#endif /* !_WIN32_WINNT_WINXP */
 #else /* _WIN32 && !EFIX64 && !EFI32 */
 
 /*