diff --git a/sphinx_d2lang/d2lang.py b/sphinx_d2lang/d2lang.py
index bf8ae4d..c34f039 100644
--- a/sphinx_d2lang/d2lang.py
+++ b/sphinx_d2lang/d2lang.py
@@ -11,9 +11,10 @@ class D2langDirective(Directive):
     def run(self):
         # TODO : add tempfile for diag_source
         outdir = self.state.document.settings.env.app.builder.outdir
+        srcdir = self.state.document.settings.env.srcdir
         diag_source = self.content
         d2_bin = which('d2')
-        cmd_line = "echo %s | %s - %s" % (diag_source, d2_bin, outdir + "/test.svg")
+        cmd_line = "echo %s | %s - %s" % (diag_source, d2_bin, srcdir + "/test.svg")
         args = shlex.split(cmd_line)
         subprocess.run(args)
         image_node = nodes.image(uri="/test.svg")