diff --git a/src/datajoint/diagram.py b/src/datajoint/diagram.py
index 20cd34b58..c51109edb 100644
--- a/src/datajoint/diagram.py
+++ b/src/datajoint/diagram.py
@@ -1496,8 +1496,19 @@ def make_dot(self):
         dot.set_rankdir(direction)
         for node in dot.get_nodes():
             node.set_shape("circle")
-            name = node.get_name().strip('"')
-            props = node_props[name]
+            # Recover the original node key. `_encapsulate_node_names` wraps every
+            # key in one layer of double quotes; a plain strip('"') over-strips
+            # when the key is itself a quoted PostgreSQL table name
+            # (`"schema"."table"`), which previously raised a KeyError below
+            # (#1535). Try candidates and pick the one that is an actual key.
+            raw = node.get_name()
+            name = next(
+                (k for k in (raw, raw.strip('"'), raw[1:-1]) if k in node_props),
+                raw.strip('"'),
+            )
+            props = node_props.get(name)
+            if props is None:
+                continue  # unknown node — leave default styling rather than crash
             node.set_fontsize(props["fontsize"])
             node.set_fontcolor(props["fontcolor"])
             node.set_shape(props["shape"])
diff --git a/tests/integration/test_diagram_nocontext.py b/tests/integration/test_diagram_nocontext.py
new file mode 100644
index 000000000..5809b8aed
--- /dev/null
+++ b/tests/integration/test_diagram_nocontext.py
@@ -0,0 +1,54 @@
+"""
+Regression test for #1535: dj.Diagram must render even when class-name
+resolution fails and nodes fall back to raw (quoted) table names — previously a
+KeyError on PostgreSQL, where `"schema"."table"` node keys were over-stripped.
+"""
+
+import time
+
+import pytest
+
+import datajoint as dj
+
+
+@pytest.fixture(scope="function")
+def schema_by_backend(connection_by_backend, db_creds_by_backend):
+    backend = db_creds_by_backend["backend"]
+    test_id = str(int(time.time() * 1000))[-8:]
+    schema_name = f"djtest_noctx_{backend}_{test_id}"[:64]
+    if connection_by_backend.is_connected:
+        try:
+            connection_by_backend.query(
+                f"DROP DATABASE IF EXISTS {connection_by_backend.adapter.quote_identifier(schema_name)}"
+            )
+        except Exception:
+            pass
+    schema = dj.Schema(schema_name, connection=connection_by_backend)
+    yield schema
+    if connection_by_backend.is_connected:
+        try:
+            connection_by_backend.query(
+                f"DROP DATABASE IF EXISTS {connection_by_backend.adapter.quote_identifier(schema_name)}"
+            )
+        except Exception:
+            pass
+
+
+def test_diagram_renders_without_context(schema_by_backend):
+    """With an empty context, nodes keep raw table names; rendering must still
+    succeed (no KeyError) on both backends."""
+    if not dj.diagram.diagram_active:
+        pytest.skip("networkx/pydot not available")
+
+    @schema_by_backend
+    class Master(dj.Manual):
+        definition = "master_id : int32"
+
+        class Part(dj.Part):
+            definition = "-> master\npart_id : int32"
+
+    # Empty context => class-name resolution fails => raw table-name nodes.
+    dot = dj.Diagram(schema_by_backend, context={}).make_dot()
+    names = [n.get_name() for n in dot.get_nodes()]
+    # The master's table appears as a node (by raw table name).
+    assert any("master" in n.lower() for n in names), f"master node missing; nodes={names}"