diff --git a/xarray/core/formatting_html.py b/xarray/core/formatting_html.py
index b03ecc12962..dbebbcf4fbe 100644
--- a/xarray/core/formatting_html.py
+++ b/xarray/core/formatting_html.py
@@ -96,7 +96,7 @@ def summarize_variable(name, var, is_index=False, dtype=None, preview=None):
     cssclass_idx = " class='xr-has-index'" if is_index else ""
     dims_str = f"({', '.join(escape(dim) for dim in var.dims)})"
     name = escape(name)
-    dtype = dtype or var.dtype
+    dtype = dtype or escape(str(var.dtype))
 
     # "unique" ids required to expand/collapse subsections
     attrs_id = "attrs-" + str(uuid.uuid4())
diff --git a/xarray/tests/test_formatting_html.py b/xarray/tests/test_formatting_html.py
index e7f54b22d06..fea24ff93f8 100644
--- a/xarray/tests/test_formatting_html.py
+++ b/xarray/tests/test_formatting_html.py
@@ -130,3 +130,5 @@ def test_repr_of_dataset(dataset):
     assert (
         formatted.count("class='xr-section-summary-in' type='checkbox'  checked>") == 3
     )
+    assert "<U4" in formatted
+    assert "<IA>" in formatted