diff --git a/include/fmt/base.h b/include/fmt/base.h
index b24f33a65b68..e7fdef43eef9 100644
--- a/include/fmt/base.h
+++ b/include/fmt/base.h
@@ -63,13 +63,6 @@
 #else
 #  define FMT_LIBCPP_VERSION 0
 #endif
-#ifdef _MSVC_STL_UPDATE
-#  define FMT_MSVC_STL_UPDATE _MSVC_STL_UPDATE
-#elif defined(_MSC_VER) && _MSC_VER < 1912  // VS 15.5
-#  define FMT_MSVC_STL_UPDATE _MSVC_LANG
-#else
-#  define FMT_MSVC_STL_UPDATE 0
-#endif
 
 // Detect __has_*.
 #ifdef __has_feature
diff --git a/include/fmt/ostream.h b/include/fmt/ostream.h
index 2ae944ff6412..5d893c92164c 100644
--- a/include/fmt/ostream.h
+++ b/include/fmt/ostream.h
@@ -22,6 +22,14 @@
 
 #include "chrono.h"  // formatbuf
 
+#ifdef _MSVC_STL_UPDATE
+#  define FMT_MSVC_STL_UPDATE _MSVC_STL_UPDATE
+#elif defined(_MSC_VER) && _MSC_VER < 1912  // VS 15.5
+#  define FMT_MSVC_STL_UPDATE _MSVC_LANG
+#else
+#  define FMT_MSVC_STL_UPDATE 0
+#endif
+
 FMT_BEGIN_NAMESPACE
 namespace detail {