diff --git a/src/regex.cpp b/src/regex.cpp
index 74146532..0a503820 100644
--- a/src/regex.cpp
+++ b/src/regex.cpp
@@ -28,7 +28,9 @@
 #endif
 #ifdef BOOST_REGEX_HAS_MS_STACK_GUARD
 #define WIN32_LEAN_AND_MEAN
-#define NOMINMAX
+#ifndef NOMINMAX
+#  define NOMINMAX
+#endif
 #define NOGDI
 #define NOUSER
 #include <windows.h>
diff --git a/src/static_mutex.cpp b/src/static_mutex.cpp
index 01eb7dd5..b01f9f0d 100644
--- a/src/static_mutex.cpp
+++ b/src/static_mutex.cpp
@@ -24,7 +24,9 @@
 #include <boost/regex/pending/static_mutex.hpp>
 
 #if defined(BOOST_HAS_WINTHREADS)
-#define NOMINMAX
+#ifndef NOMINMAX
+#  define NOMINMAX
+#endif
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 #include <boost/static_assert.hpp>
diff --git a/src/w32_regex_traits.cpp b/src/w32_regex_traits.cpp
index 20e84d15..64fd2ce4 100644
--- a/src/w32_regex_traits.cpp
+++ b/src/w32_regex_traits.cpp
@@ -24,7 +24,9 @@
 #include <boost/regex/pattern_except.hpp>
 
 #define WIN32_LEAN_AND_MEAN
-#define NOMINMAX
+#ifndef NOMINMAX
+#  define NOMINMAX
+#endif
 #define NOGDI
 #include <windows.h>