diff --git a/lib/chibi/filesystem.stub b/lib/chibi/filesystem.stub
index a82af25e..29b35810 100644
--- a/lib/chibi/filesystem.stub
+++ b/lib/chibi/filesystem.stub
@@ -14,6 +14,7 @@
 
 (cond-expand
   (windows
+   (c-include-verbatim "filesystem_win32_shim.c")
    (define-c-struct stat
     predicate: stat?
     (dev_t      st_dev      stat-dev)
@@ -30,10 +31,6 @@
     (time_t     st_mtime    stat-mtime)
     (time_t     st_ctime    stat-ctime)))
   (else
-   (define-c-type DIR
-    finalizer: closedir)
-   (define-c-struct dirent
-    (string d_name dirent-name))
    (define-c-struct stat
     predicate: stat?
     (dev_t      st_dev      stat-dev)
@@ -51,18 +48,19 @@
     (time_t     st_ctime    stat-ctime))
    ))
 
+(define-c-type DIR
+ finalizer: closedir)
+(define-c-struct dirent
+ (string d_name dirent-name))
 
 
-
-(cond-expand
-  ((not windows)
-   (define-c boolean S_ISREG (mode_t))
-   (define-c boolean S_ISDIR (mode_t))
-   (define-c boolean S_ISCHR (mode_t))
-   (define-c boolean S_ISBLK (mode_t))
-   (define-c boolean S_ISFIFO (mode_t))
-   (define-c boolean S_ISLNK (mode_t))
-   (define-c boolean S_ISSOCK (mode_t))))
+(define-c boolean S_ISREG (mode_t))
+(define-c boolean S_ISDIR (mode_t))
+(define-c boolean S_ISCHR (mode_t))
+(define-c boolean S_ISBLK (mode_t))
+(define-c boolean S_ISFIFO (mode_t))
+(define-c boolean S_ISLNK (mode_t))
+(define-c boolean S_ISSOCK (mode_t))
 
 (cond-expand
  ((not windows)
@@ -152,7 +150,7 @@
   ((not windows)
    (define-c errno (create-directory "mkdir") (string (default #o775 int))))
   (else
-   (define-c errno (create-directory "mkdir") (string))))
+   (define-c errno (create-directory "mkdir_shim") (string (default #o775 int)))))
 
 ;;> Deletes the directory named \var{string} from the filesystem.
 ;;> Does not attempt to delete recursively.
@@ -160,10 +158,8 @@
 
 (define-c errno (delete-directory "rmdir") (string))
 
-(cond-expand
-  ((not windows)
-   (define-c (free DIR) opendir (string))
-   (define-c dirent readdir ((link (pointer DIR))))))
+(define-c (free DIR) opendir (string))
+(define-c dirent readdir ((link (pointer DIR))))
 
 ;;> Duplicates the given file descriptor, returning he new value,
 ;; or -1 on failure.
@@ -248,11 +244,9 @@
     (port-or-fileno off_t))))
 
 ;; Used for file-is-readable?, file-is-writable?, file-is-executable?.
-(cond-expand
-  ((not windows)
-   (define-c-const int (access/read "R_OK"))
-   (define-c-const int (access/write "W_OK"))
-   (define-c-const int (access/execute "X_OK"))))
+(define-c-const int (access/read "R_OK"))
+(define-c-const int (access/write "W_OK"))
+(define-c-const int (access/execute "X_OK"))
 (define-c int (file-access "access") (string int))
 
 ;;> Applies the specified locking operation using flock(2) to the port
diff --git a/lib/chibi/filesystem_win32_shim.c b/lib/chibi/filesystem_win32_shim.c
new file mode 100644
index 00000000..49429c15
--- /dev/null
+++ b/lib/chibi/filesystem_win32_shim.c
@@ -0,0 +1,104 @@
+/* Win32 shim for (chibi filesystem) */
+
+#include <windows.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <direct.h>
+
+static int mkdir_shim(const char* path, int ignored) {
+    return mkdir(path);
+}
+
+#if !defined(__MINGW32__) && !defined(__MINGW64__)
+/* Flags for _access() API */
+#define R_OK 4
+#define W_OK 2
+#define X_OK 1 /* Follow MinGW */
+
+#define SHIM_WIN32_STAT_IS(m, flg) ((m & _S_IFMT) == flg)
+#define S_ISREG(m) SHIM_WIN32_STAT_IS(m, _S_IFREG)
+#define S_ISDIR(m) SHIM_WIN32_STAT_IS(m, _S_IFDIR)
+#define S_ISCHR(m) SHIM_WIN32_STAT_IS(m, _S_IFCHR)
+#define S_ISFIFO(m) SHIM_WIN32_STAT_IS(m, _S_IFIFO)
+#define S_ISBLK(m) 0
+#endif
+
+#define S_ISLNK(m) 0
+#define S_ISSOCK(m) S_ISFIFO(m)
+
+struct dirent {
+    char d_name[MAX_PATH];
+};
+
+struct DIR_s {
+    int want_next;
+    HANDLE hFind;
+    struct dirent result;
+};
+
+typedef struct DIR_s DIR;
+
+static DIR* opendir(const char* path) {
+    HANDLE hFind;
+    WIN32_FIND_DATAA ffd;
+    DIR* dp;
+    char* query;
+    query = malloc(MAX_PATH + 1);
+    if(!query){
+        errno = ENOMEM;
+        return NULL;
+    }
+    query[0] = 0;
+    strncat(query, path, MAX_PATH);
+    strncat(query, "\\*", MAX_PATH);
+    query[MAX_PATH] = 0;
+    hFind = FindFirstFileA(query, &ffd);
+    if(hFind == INVALID_HANDLE_VALUE){
+        switch(GetLastError()){
+            case ERROR_FILE_NOT_FOUND:
+                errno = ENOENT;
+                break;
+            default:
+                errno = EACCES;
+                break;
+        }
+        return NULL;
+    }
+    free(query);
+    dp = malloc(sizeof(DIR));
+    if(!dp){
+        errno = ENOMEM;
+        return NULL;
+    }
+    dp->hFind = hFind;
+    strncpy(dp->result.d_name, ffd.cFileName, MAX_PATH);
+    dp->want_next = 0;
+    return dp;
+}
+
+static struct dirent *readdir(DIR *dp) {
+    BOOL b;
+    WIN32_FIND_DATAA ffd;
+    if(dp->want_next){
+        /* Query the next file */
+        b = FindNextFile(dp->hFind, &ffd);
+        if(! b){
+            return NULL;
+        }
+        strncpy(dp->result.d_name, ffd.cFileName, MAX_PATH);
+    }
+    dp->want_next = 1;
+    return &dp->result;
+}
+
+static int closedir(DIR *dp) {
+    BOOL b;
+    b = FindClose(dp->hFind);
+    if(! b){
+        errno = EBADF;
+        return -1;
+    }
+    free(dp);
+    return 0;
+}