diff --git a/tools/buildman/README b/tools/buildman/README
index f3a0dc7..b2f983c 100644
--- a/tools/buildman/README
+++ b/tools/buildman/README
@@ -1091,7 +1091,8 @@
 
    buildman -o /tmp/build --board sandbox -w
 
-This will write the full build into /tmp/build including object files.
+This will write the full build into /tmp/build including object files. You must
+specify the output directory with -o when using -w.
 
 
 Other options
diff --git a/tools/buildman/cmdline.py b/tools/buildman/cmdline.py
index 1377b9d..680c072 100644
--- a/tools/buildman/cmdline.py
+++ b/tools/buildman/cmdline.py
@@ -76,8 +76,7 @@
           default=False, help="Do a dry run (describe actions, but do nothing)")
     parser.add_option('-N', '--no-subdirs', action='store_true', dest='no_subdirs',
           default=False, help="Don't create subdirectories when building current source for a single board")
-    parser.add_option('-o', '--output-dir', type='string',
-          dest='output_dir', default='..',
+    parser.add_option('-o', '--output-dir', type='string', dest='output_dir',
           help='Directory where all builds happen and buildman has its workspace (default is ../)')
     parser.add_option('-O', '--override-toolchain', type='string',
           help="Override host toochain to use for sandbox (e.g. 'clang-7')")
diff --git a/tools/buildman/control.py b/tools/buildman/control.py
index 7ee0368..7c8d752 100644
--- a/tools/buildman/control.py
+++ b/tools/buildman/control.py
@@ -175,6 +175,10 @@
     if options.incremental:
         print(col.Color(col.RED,
                         'Warning: -I has been removed. See documentation'))
+    if not options.output_dir:
+        if options.work_in_output:
+            sys.exit(col.Color(col.RED, '-w requires that you specify -o'))
+        options.output_dir = '..'
 
     # Work out what subset of the boards we are building
     if not boards:
diff --git a/tools/buildman/func_test.py b/tools/buildman/func_test.py
index 1fbc6f6..8d3325d 100644
--- a/tools/buildman/func_test.py
+++ b/tools/buildman/func_test.py
@@ -569,3 +569,9 @@
             self._RunControl('-b', self._test_branch, '-o', self._output_dir,
                              '-w', clean_dir=False, boards=board_list)
         self.assertIn("single commit", str(e.exception))
+
+        board_list = board.Boards()
+        board_list.AddBoard(board.Board(*boards[0]))
+        with self.assertRaises(SystemExit) as e:
+            self._RunControl('-w', clean_dir=False)
+        self.assertIn("specify -o", str(e.exception))