diff --git a/source/common/putil.cpp b/source/common/putil.cpp
index ab25f3b..94782f8 100644
--- a/source/common/putil.cpp
+++ b/source/common/putil.cpp
@@ -48,7 +48,6 @@
 
 #if U_PLATFORM == U_PF_MINGW && defined __STRICT_ANSI__
 /* tzset isn't defined in strict ANSI on MinGW. */
-#undef __STRICT_ANSI__
 #endif
 
 /*
