diff --git a/libraries/AP_HAL_SITL/SITL_cmdline.cpp b/libraries/AP_HAL_SITL/SITL_cmdline.cpp
index 08935725b5..4a6185615f 100644
--- a/libraries/AP_HAL_SITL/SITL_cmdline.cpp
+++ b/libraries/AP_HAL_SITL/SITL_cmdline.cpp
@@ -42,6 +42,7 @@ void SITL_State::_usage(void)
            "\t--instance N       set instance of SITL (adds 10*instance to all port numbers)\n"
            "\t--speedup SPEEDUP  set simulation speedup\n"
            "\t--gimbal           enable simulated MAVLink gimbal\n"
+           "\t--autotest-dir DIR set directory for additional files\n"
         );
 }
 
@@ -67,8 +68,11 @@ void SITL_State::_parse_command_line(int argc, char * const argv[])
     int opt;
     const char *home_str = NULL;
     const char *model_str = NULL;
+    char *autotest_dir = NULL;
     float speedup = 1.0f;
 
+    asprintf(&autotest_dir, SKETCHBOOK "/Tools/autotest");
+
     signal(SIGFPE, _sig_fpe);
     // No-op SIGPIPE handler
     signal(SIGPIPE, SIG_IGN);
@@ -86,7 +90,8 @@ void SITL_State::_parse_command_line(int argc, char * const argv[])
 
     enum long_options {
         CMDLINE_CLIENT=0,
-        CMDLINE_GIMBAL
+        CMDLINE_GIMBAL,
+        CMDLINE_AUTOTESTDIR
     };
 
     const struct GetOptLong::option options[] = {
@@ -102,6 +107,7 @@ void SITL_State::_parse_command_line(int argc, char * const argv[])
         {"model",           true,   0, 'M'},
         {"client",          true,   0, CMDLINE_CLIENT},
         {"gimbal",          false,  0, CMDLINE_GIMBAL},
+        {"autotest-dir",    true,   0, CMDLINE_AUTOTESTDIR},
         {0, false, 0, 0}
     };
 
@@ -151,6 +157,9 @@ void SITL_State::_parse_command_line(int argc, char * const argv[])
         case CMDLINE_GIMBAL:
             enable_gimbal = true;
             break;
+        case CMDLINE_AUTOTESTDIR:
+            autotest_dir = strdup(gopt.optarg);
+            break;
         default:
             _usage();
             exit(1);
@@ -163,6 +172,7 @@ void SITL_State::_parse_command_line(int argc, char * const argv[])
                 sitl_model = model_constructors[i].constructor(home_str, model_str);
                 sitl_model->set_speedup(speedup);
                 sitl_model->set_instance(_instance);
+                sitl_model->set_autotest_dir(autotest_dir);
                 _synthetic_clock_mode = true;
                 printf("Started model %s at %s at speed %.1f\n", model_str, home_str, speedup);
                 break;