--- source/common/umutex.h
+++ source/common/umutex.h
@@ -54,15 +54,15 @@
 
 #include <atomic>
 
-U_NAMESPACE_BEGIN
-
 // Export an explicit template instantiation of std::atomic<int32_t>. 
 // When building DLLs for Windows this is required as it is used as a data member of the exported SharedObject class.
 // See digitlst.h, pluralaffix.h, datefmt.h, and others for similar examples.
 #if U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_CYGWIN
 template struct U_COMMON_API std::atomic<int32_t>;
 #endif
 
+U_NAMESPACE_BEGIN
+
 typedef std::atomic<int32_t> u_atomic_int32_t;
 #define ATOMIC_INT32_T_INITIALIZER(val) ATOMIC_VAR_INIT(val)
 
--- source/i18n/unicode/numberrangeformatter.h
+++ source/i18n/unicode/numberrangeformatter.h
@@ -186,7 +186,13 @@
  * (When building DLLs for Windows this is required.)
  */
 #if U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_CYGWIN && !defined(U_IN_DOXYGEN)
-template struct U_I18N_API std::atomic<impl::NumberRangeFormatterImpl*>;
+} // namespace number
+U_NAMESPACE_END
+
+template struct U_I18N_API std::atomic< U_NAMESPACE_QUALIFIER number::impl::NumberRangeFormatterImpl*>;
+
+U_NAMESPACE_BEGIN
+namespace number {  // icu::number
 #endif
 /** \endcond */