diff --git a/posix.cc b/posix.cc
index 4f20c6a9..c3aabffc 100644
--- a/posix.cc
+++ b/posix.cc
@@ -34,6 +34,7 @@
 #ifndef _WIN32
 # include <unistd.h>
 #else
+# define _CRT_SECURE_NO_WARNINGS
 # include <windows.h>
 # include <io.h>
 
diff --git a/test/posix-test.cc b/test/posix-test.cc
index b4ce88e3..75e6af32 100644
--- a/test/posix-test.cc
+++ b/test/posix-test.cc
@@ -32,6 +32,7 @@
 #include <climits>
 
 #ifdef _WIN32
+# define _CRT_SECURE_NO_WARNINGS
 # include <io.h>
 # undef max
 # undef ERROR