diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index 2445031..87054c7 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -39,10 +39,19 @@
 #error "mbed TLS requires a platform with 8-bit chars"
 #endif
 
-#if defined(_WIN32) && !defined(MBEDTLS_PLATFORM_C)
+#if defined(_WIN32)
+#if !defined(MBEDTLS_PLATFORM_C)
 #error "MBEDTLS_PLATFORM_C is required on Windows"
 #endif
 
+/* Fix the config here. Not convenient to put an #ifdef _WIN32 in config.h as
+ * it would confuse config.pl. */
+#if !defined(MBEDTLS_PLATFORM_SNPRINTF_ALT) && \
+    !defined(MBEDTLS_PLATFORM_SNPRINTF_MACRO)
+#define MBEDTLS_PLATFORM_SNPRINTF_ALT
+#endif
+#endif /* _WIN32 */
+
 #if defined(MBEDTLS_DEPRECATED_WARNING) && \
     !defined(__GNUC__) && !defined(__clang__)
 #error "MBEDTLS_DEPRECATED_WARNING only works with GCC and Clang"
@@ -286,11 +295,6 @@
 #error "MBEDTLS_PLATFORM_SNPRINTF_ALT defined, but not all prerequisites"
 #endif
 
-#if defined(MBEDTLS_PLATFORM_SNPRINTF_ALT) && ( defined(_WIN32)\
-    && !defined(EFIX64) && !defined(EFI32) )
-#error "MBEDTLS_PLATFORM_SNPRINTF_ALT defined but not available on Windows"
-#endif
-
 #if defined(MBEDTLS_PLATFORM_SNPRINTF_MACRO) && !defined(MBEDTLS_PLATFORM_C)
 #error "MBEDTLS_PLATFORM_SNPRINTF_MACRO defined, but not all prerequisites"
 #endif
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 685baf2..27c139b 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -142,6 +142,9 @@
  *
  * All these define require MBEDTLS_PLATFORM_C to be defined!
  *
+ * \note MBEDTLS_PLATFORM_SNPRINTF_ALT is required on Windows;
+ * it will be enabled automatically by check_config.h
+ *
  * \warning MBEDTLS_PLATFORM_XXX_ALT cannot be defined at the same time as
  * MBEDTLS_PLATFORM_XXX_MACRO!
  *