diff --git a/src/humanize/time.py b/src/humanize/time.py
index 373657d..22dbb1e 100644
--- a/src/humanize/time.py
+++ b/src/humanize/time.py
@@ -202,7 +202,7 @@ def naturaldelta(
         else:
             return _ngettext("1 year, %d day", "1 year, %d days", days) % days
 
-    return _ngettext("%s year", "%s years", years) % intcomma(years)
+    return _ngettext("%d year", "%d years", years).replace("%d", "%s") % intcomma(years)
 
 
 def naturaltime(
diff --git a/tests/test_i18n.py b/tests/test_i18n.py
index 8b64696..e4f30f0 100644
--- a/tests/test_i18n.py
+++ b/tests/test_i18n.py
@@ -53,6 +53,25 @@ def test_intcomma() -> None:
         assert humanize.intcomma(number) == "10,000,000"
 
 
+def test_naturaldelta() -> None:
+    seconds = 1234 * 365 * 24 * 60 * 60
+
+    assert humanize.naturaldelta(seconds) == "1,234 years"
+
+    try:
+        humanize.i18n.activate("fr_FR")
+        assert humanize.naturaldelta(seconds) == "1 234 ans"
+        humanize.i18n.activate("es_ES")
+        assert humanize.naturaldelta(seconds) == "1,234 años"
+
+    except FileNotFoundError:
+        pytest.skip("Generate .mo with scripts/generate-translation-binaries.sh")
+
+    finally:
+        humanize.i18n.deactivate()
+        assert humanize.naturaldelta(seconds) == "1,234 years"
+
+
 @pytest.mark.parametrize(
     ("locale", "number", "expected_result"),
     (