diff --git a/libraries/AP_Filesystem/AP_Filesystem_posix.cpp b/libraries/AP_Filesystem/AP_Filesystem_posix.cpp
index 6c7b4cca05..042bcf2db3 100644
--- a/libraries/AP_Filesystem/AP_Filesystem_posix.cpp
+++ b/libraries/AP_Filesystem/AP_Filesystem_posix.cpp
@@ -29,8 +29,28 @@
 
 extern const AP_HAL::HAL& hal;
 
+/*
+  map a filename for SITL so operations are relative to the current directory
+ */
+static const char *map_filename(const char *fname)
+{
+#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
+    // on SITL only allow paths under subdirectory. Users can still
+    // escape with .. if they want to
+    if (strcmp(fname, "/") == 0) {
+        return ".";
+    }
+    if (*fname == '/') {
+        fname++;
+    }
+#endif
+    // on Linux allow original name
+    return fname;
+}
+
 int AP_Filesystem::open(const char *fname, int flags)
 {
+    fname = map_filename(fname);
     // we automatically add O_CLOEXEC as we always want it for ArduPilot FS usage
     return ::open(fname, flags | O_CLOEXEC, 0644);
 }
@@ -62,11 +82,13 @@ off_t AP_Filesystem::lseek(int fd, off_t offset, int seek_from)
 
 int AP_Filesystem::stat(const char *pathname, struct stat *stbuf)
 {
+    pathname = map_filename(pathname);
     return ::stat(pathname, stbuf);
 }
 
 int AP_Filesystem::unlink(const char *pathname)
 {
+    pathname = map_filename(pathname);
     // we match the FATFS interface and use unlink
     // for both files and directories
     int ret = ::rmdir(pathname);
@@ -78,11 +100,13 @@ int AP_Filesystem::unlink(const char *pathname)
 
 int AP_Filesystem::mkdir(const char *pathname)
 {
+    pathname = map_filename(pathname);
     return ::mkdir(pathname, 0775);
 }
 
 DIR *AP_Filesystem::opendir(const char *pathname)
 {
+    pathname = map_filename(pathname);
     return ::opendir(pathname);
 }
 
@@ -99,6 +123,7 @@ int AP_Filesystem::closedir(DIR *dirp)
 // return free disk space in bytes
 int64_t AP_Filesystem::disk_free(const char *path)
 {
+    path = map_filename(path);
     struct statfs stats;
     if (::statfs(path, &stats) < 0) {
         return -1;
@@ -109,6 +134,7 @@ int64_t AP_Filesystem::disk_free(const char *path)
 // return total disk space in bytes
 int64_t AP_Filesystem::disk_space(const char *path)
 {
+    path = map_filename(path);
     struct statfs stats;
     if (::statfs(path, &stats) < 0) {
         return -1;
@@ -122,6 +148,7 @@ int64_t AP_Filesystem::disk_space(const char *path)
  */
 bool AP_Filesystem::set_mtime(const char *filename, const time_t mtime_sec)
 {
+    filename = map_filename(filename);
     struct utimbuf times {};
     times.actime = mtime_sec;
     times.modtime = mtime_sec;