diff --git a/HISTORY.rst b/HISTORY.rst
index 84ee3562..32e2aa8d 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -4,6 +4,11 @@ Release Notes
 PlatformIO 3.0
 --------------
 
+3.6.6 (2019-??-??)
+~~~~~~~~~~~~~~~~~~
+
+* Fixed "FileExistsError" when `platformio ci <https://docs.platformio.org/en/latest/userguide/cmd_ci.html>`__ command is used in pair with ``--keep-build-dir`` option
+
 3.6.5 (2019-03-07)
 ~~~~~~~~~~~~~~~~~~
 
diff --git a/platformio/commands/ci.py b/platformio/commands/ci.py
index 0b5b3e4e..13224fac 100644
--- a/platformio/commands/ci.py
+++ b/platformio/commands/ci.py
@@ -55,7 +55,6 @@ def validate_path(ctx, param, value):  # pylint: disable=unused-argument
     "--build-dir",
     default=mkdtemp,
     type=click.Path(
-        exists=True,
         file_okay=False,
         dir_okay=True,
         writable=True,
@@ -134,7 +133,8 @@ def _copy_contents(dst_dir, contents):
     if dst_dir_name == "src" and len(items['dirs']) == 1:
         copytree(list(items['dirs']).pop(), dst_dir, symlinks=True)
     else:
-        makedirs(dst_dir)
+        if not isdir(dst_dir):
+            makedirs(dst_dir)
         for d in items['dirs']:
             copytree(d, join(dst_dir, basename(d)), symlinks=True)
 
diff --git a/tests/commands/test_ci.py b/tests/commands/test_ci.py
index ec4077ba..67ff4420 100644
--- a/tests/commands/test_ci.py
+++ b/tests/commands/test_ci.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from os.path import join
+from os.path import isfile, join
 
 from platformio.commands.ci import cli as cmd_ci
 from platformio.commands.lib import cli as cmd_lib
@@ -32,6 +32,36 @@ def test_ci_boards(clirunner, validate_cliresult):
     validate_cliresult(result)
 
 
+def test_ci_build_dir(clirunner, tmpdir_factory, validate_cliresult):
+    build_dir = str(tmpdir_factory.mktemp("ci_build_dir"))
+    result = clirunner.invoke(cmd_ci, [
+        join("examples", "wiring-blink", "src", "main.cpp"), "-b", "uno",
+        "--build-dir", build_dir
+    ])
+    validate_cliresult(result)
+    assert not isfile(join(build_dir, "platformio.ini"))
+
+
+def test_ci_keep_build_dir(clirunner, tmpdir_factory, validate_cliresult):
+    build_dir = str(tmpdir_factory.mktemp("ci_build_dir"))
+    result = clirunner.invoke(cmd_ci, [
+        join("examples", "wiring-blink", "src", "main.cpp"), "-b", "uno",
+        "--build-dir", build_dir, "--keep-build-dir"
+    ])
+    validate_cliresult(result)
+    assert isfile(join(build_dir, "platformio.ini"))
+
+    # 2nd attempt
+    result = clirunner.invoke(cmd_ci, [
+        join("examples", "wiring-blink", "src", "main.cpp"), "-b", "metro",
+        "--build-dir", build_dir, "--keep-build-dir"
+    ])
+    validate_cliresult(result)
+
+    assert "board: uno" in result.output
+    assert "board: metro" in result.output
+
+
 def test_ci_project_conf(clirunner, validate_cliresult):
     project_dir = join("examples", "wiring-blink")
     result = clirunner.invoke(cmd_ci, [