diff --git a/sphinx_d2lang/d2lang.py b/sphinx_d2lang/d2lang.py
index 0a0d40e..5b02c40 100644
--- a/sphinx_d2lang/d2lang.py
+++ b/sphinx_d2lang/d2lang.py
@@ -4,6 +4,7 @@ from docutils.parsers.rst import Directive
 
 from shutil import which
 import shlex
+import subprocess
 
 class D2langDirective(Directive):
     has_content = True