diff --git a/paperqa/types.py b/paperqa/types.py
index d1ab001a9..ed1384c8f 100644
--- a/paperqa/types.py
+++ b/paperqa/types.py
@@ -54,6 +54,9 @@ class Doc(Embeddable):
     citation: str
     dockey: DocKey
 
+    def __hash__(self) -> int:
+        return hash((self.docname, self.dockey))
+
 
 class Text(Embeddable):
     text: str
diff --git a/tests/test_paperqa.py b/tests/test_paperqa.py
index dc6733e77..189fc7347 100644
--- a/tests/test_paperqa.py
+++ b/tests/test_paperqa.py
@@ -641,21 +641,31 @@ async def my_callback(result):
     assert len(my_results) > 1
 
 
-def test_duplicate():
+def test_duplicate() -> None:
+    """Check Docs doesn't store duplicates, while checking nonduplicate docs are stored."""
     docs = Docs()
     assert docs.add_url(
         "https://en.wikipedia.org/wiki/Frederick_Bates_(politician)",
         citation="WikiMedia Foundation, 2023, Accessed now",
-        dockey="test",
+        dockey="test1",
     )
     assert (
         docs.add_url(
             "https://en.wikipedia.org/wiki/Frederick_Bates_(politician)",
             citation="WikiMedia Foundation, 2023, Accessed now",
-            dockey="test",
+            dockey="test1",
         )
         is None
     )
+    assert len(docs.docs) == 1, "Should have added only one document"
+    assert docs.add_url(
+        "https://en.wikipedia.org/wiki/National_Flag_of_Canada_Day",
+        citation="WikiMedia Foundation, 2023, Accessed now",
+        dockey="test2",
+    )
+    assert (
+        len(set(docs.docs.values())) == 2
+    ), "Unique documents should be hashed as unique"
 
 
 def test_custom_embedding():