diff --git a/crypto/compat/posix_win.c b/crypto/compat/posix_win.c
index 05a20bb..331f88e 100644
--- a/crypto/compat/posix_win.c
+++ b/crypto/compat/posix_win.c
@@ -12,6 +12,7 @@
 #include <ws2tcpip.h>
 
 #include <errno.h>
+#include <fcntl.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -39,6 +40,28 @@ posix_fopen(const char *path, const char *mode)
 	return fopen(path, mode);
 }
 
+int
+posix_open(const char *path, ...)
+{
+	va_list ap;
+	mode_t mode = 0;
+	int flags;
+
+	va_start(ap, path);
+	flags = va_arg(ap, int);
+	if (flags & O_CREAT)
+		mode = va_arg(ap, int);
+	va_end(ap);
+
+	flags |= O_BINARY;
+	if (flags & O_CLOEXEC) {
+		flags &= ~O_CLOEXEC;
+		flags |= O_NOINHERIT;
+	}
+	flags &= ~O_NONBLOCK;
+	return open(path, flags, mode);
+}
+
 char *
 posix_fgets(char *s, int size, FILE *stream)
 {
diff --git a/crypto/crypto_win.list b/crypto/crypto_win.list
index 6f89a43..37c02a5 100644
--- a/crypto/crypto_win.list
+++ b/crypto/crypto_win.list
@@ -7,6 +7,7 @@ posix_close
 posix_connect
 posix_fgets
 posix_fopen
+posix_open
 posix_read
 posix_rename
 posix_write
diff --git a/include/compat/fcntl.h b/include/compat/fcntl.h
index 99c2d58..edc468a 100644
--- a/include/compat/fcntl.h
+++ b/include/compat/fcntl.h
@@ -29,4 +29,10 @@
 #define FD_CLOEXEC      1
 #endif
 
+int posix_open(const char *path, ...);
+
+#ifndef NO_REDEF_POSIX_FUNCTIONS
+#define open(path, ...) posix_open(path, __VA_ARGS__)
+#endif
+
 #endif
diff --git a/m4/check-libc.m4 b/m4/check-libc.m4
index 54efc37..3c0ed31 100644
--- a/m4/check-libc.m4
+++ b/m4/check-libc.m4
@@ -201,6 +201,7 @@ if test "x$HOST_OS" = "xwin" ; then
 	echo posix_perror >> $crypto_p_sym
 	echo posix_fopen >> $crypto_p_sym
 	echo posix_fgets >> $crypto_p_sym
+	echo posix_open >> $crypto_p_sym
 	echo posix_rename >> $crypto_p_sym
 	echo posix_connect >> $crypto_p_sym
 	echo posix_close >> $crypto_p_sym