diff --git a/cloudinit/templater.py b/cloudinit/templater.py
index 1e147d4ab64..d8af5096062 100644
--- a/cloudinit/templater.py
+++ b/cloudinit/templater.py
@@ -104,7 +104,10 @@ def jinja_render(content, params):
         add = "\n" if content.endswith("\n") else ""
         return (
             JTemplate(
-                content, undefined=UndefinedJinjaVariable, trim_blocks=True
+                content,
+                undefined=UndefinedJinjaVariable,
+                trim_blocks=True,
+                extensions=["jinja2.ext.do"],
             ).render(**params)
             + add
         )
diff --git a/tests/unittests/test_templating.py b/tests/unittests/test_templating.py
index c1fec27c434..3a0195bf292 100644
--- a/tests/unittests/test_templating.py
+++ b/tests/unittests/test_templating.py
@@ -184,5 +184,19 @@ def test_jinja_warns_on_missing_dep_and_uses_basic_renderer(self):
             self.logs.getvalue(),
         )
 
+    def test_jinja_do_extension_render_to_string(self):
+        """Test jinja render_to_string using do extension."""
+        expected_result = "[1, 2, 3]"
+        jinja_template = (
+            "{% set r = [] %} {% set input = [1,2,3] %} "
+            "{% for i in input %} {% do r.append(i) %} {% endfor %} {{r}}"
+        )
+        self.assertEqual(
+            templater.render_string(
+                self.add_header("jinja", jinja_template), {}
+            ).strip(),
+            expected_result,
+        )
+
 
 # vi: ts=4 expandtab
diff --git a/tools/.github-cla-signers b/tools/.github-cla-signers
index 0567a89dfc3..1aaae7f9a9f 100644
--- a/tools/.github-cla-signers
+++ b/tools/.github-cla-signers
@@ -79,6 +79,7 @@ steverweber
 t-8ch
 TheRealFalcon
 taoyama
+thetoolsmith
 timothegenzmer
 tnt-dev
 tomponline