diff --git a/libavformat/os_support.h b/libavformat/os_support.h
index 50846d0f41..4aa98bdc18 100644
--- a/libavformat/os_support.h
+++ b/libavformat/os_support.h
@@ -127,24 +127,7 @@ int ff_poll(struct pollfd *fds, nfds_t numfds, int timeout);
 #elif defined(_WIN32)
 #include <stdio.h>
 #include <windows.h>
-#include "libavutil/mem.h"
-
-static inline int utf8towchar(const char *filename_utf8, wchar_t **filename_w)
-{
-    int num_chars;
-    num_chars = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, filename_utf8, -1, NULL, 0);
-    if (num_chars <= 0) {
-        *filename_w = NULL;
-        return 0;
-    }
-    *filename_w = av_mallocz(sizeof(wchar_t) * num_chars);
-    if (!*filename_w) {
-        errno = ENOMEM;
-        return -1;
-    }
-    MultiByteToWideChar(CP_UTF8, 0, filename_utf8, -1, *filename_w, num_chars);
-    return 0;
-}
+#include "libavutil/wchar_filename.h"
 
 #define DEF_FS_FUNCTION(name, wfunc, afunc)               \
 static inline int win32_##name(const char *filename_utf8) \
diff --git a/libavutil/file_open.c b/libavutil/file_open.c
index 765eb60ef3..f14ea70862 100644
--- a/libavutil/file_open.c
+++ b/libavutil/file_open.c
@@ -37,23 +37,18 @@
 #include <windows.h>
 #include <share.h>
 #include <errno.h>
+#include "wchar_filename.h"
 
 static int win32_open(const char *filename_utf8, int oflag, int pmode)
 {
     int fd;
-    int num_chars;
     wchar_t *filename_w;
 
     /* convert UTF-8 to wide chars */
-    num_chars = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, filename_utf8, -1, NULL, 0);
-    if (num_chars <= 0)
-        goto fallback;
-    filename_w = av_mallocz(sizeof(wchar_t) * num_chars);
-    if (!filename_w) {
-        errno = ENOMEM;
+    if (utf8towchar(filename_utf8, &filename_w))
         return -1;
-    }
-    MultiByteToWideChar(CP_UTF8, 0, filename_utf8, -1, filename_w, num_chars);
+    if (!filename_w)
+        goto fallback;
 
     fd = _wsopen(filename_w, oflag, SH_DENYNO, pmode);
     av_freep(&filename_w);
diff --git a/libavutil/wchar_filename.h b/libavutil/wchar_filename.h
new file mode 100644
index 0000000000..2781773dee
--- /dev/null
+++ b/libavutil/wchar_filename.h
@@ -0,0 +1,44 @@
+/*
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_WCHAR_FILENAME_H
+#define AVUTIL_WCHAR_FILENAME_H
+
+#if defined(_WIN32) && !defined(__MINGW32CE__)
+#include <windows.h>
+#include "mem.h"
+
+static inline int utf8towchar(const char *filename_utf8, wchar_t **filename_w)
+{
+    int num_chars;
+    num_chars = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, filename_utf8, -1, NULL, 0);
+    if (num_chars <= 0) {
+        *filename_w = NULL;
+        return 0;
+    }
+    *filename_w = av_mallocz(sizeof(wchar_t) * num_chars);
+    if (!*filename_w) {
+        errno = ENOMEM;
+        return -1;
+    }
+    MultiByteToWideChar(CP_UTF8, 0, filename_utf8, -1, *filename_w, num_chars);
+    return 0;
+}
+#endif
+
+#endif /* AVUTIL_WCHAR_FILENAME_H */