diff --git a/spacy/tests/doc/test_underscore.py b/spacy/tests/doc/test_underscore.py
index a62010820..96ddb730a 100644
--- a/spacy/tests/doc/test_underscore.py
+++ b/spacy/tests/doc/test_underscore.py
@@ -348,3 +348,118 @@ def test_underscore_for_unique_span(en_tokenizer):
     # Assert extensions with original key
     assert doc.user_data[("._.", "doc_extension", None, None)] == "doc extension"
     assert doc.user_data[("._.", "token_extension", 0, None)] == "token extension"
+
+def test_underscore_for_unique_span_from_docs(en_tokenizer):
+    """Test that spans in the user_data keep the same data structure"""
+    Span.set_extension(name="span_extension", default=None)
+    Token.set_extension(name="token_extension", default=None)
+
+    # Initialize doc
+    text_1 = "Hello, world!"
+    doc_1 = en_tokenizer(text_1)
+    span_1a = Span(doc_1, 0, 2, "SPAN_1a")
+    span_1b = Span(doc_1, 0, 2, "SPAN_1b")
+
+    text_2 = "This is a test."
+    doc_2 = en_tokenizer(text_2)
+    span_2a = Span(doc_2, 0, 3, "SPAN_2a")
+
+    # Set custom extensions
+    doc_1[0]._.token_extension = "token_1"
+    doc_2[1]._.token_extension = "token_2"
+    span_1a._.span_extension = "span_1a extension"
+    span_1b._.span_extension = "span_1b extension"
+    span_2a._.span_extension = "span_2a extension"
+
+    doc = Doc.from_docs([doc_1,doc_2])
+    # Assert extensions
+    assert (
+        doc_1.user_data[
+            (
+                "._.",
+                "span_extension",
+                span_1a.start_char,
+                span_1a.end_char,
+                span_1a.label,
+                span_1a.kb_id,
+                span_1a.id,
+            )
+        ]
+        == "span_1a extension"
+    )
+
+    assert (
+        doc_1.user_data[
+            (
+                "._.",
+                "span_extension",
+                span_1b.start_char,
+                span_1b.end_char,
+                span_1b.label,
+                span_1b.kb_id,
+                span_1b.id,
+            )
+        ]
+        == "span_1b extension"
+    )
+
+    assert (
+        doc_2.user_data[
+            (
+                "._.",
+                "span_extension",
+                span_2a.start_char,
+                span_2a.end_char,
+                span_2a.label,
+                span_2a.kb_id,
+                span_2a.id,
+            )
+        ]
+        == "span_2a extension"
+    )
+
+    # Check merged doc
+    assert (
+        doc.user_data[
+            (
+                "._.",
+                "span_extension",
+                span_1a.start_char,
+                span_1a.end_char,
+                span_1a.label,
+                span_1a.kb_id,
+                span_1a.id,
+            )
+        ]
+        == "span_1a extension"
+    )
+
+    assert (
+        doc.user_data[
+            (
+                "._.",
+                "span_extension",
+                span_1b.start_char,
+                span_1b.end_char,
+                span_1b.label,
+                span_1b.kb_id,
+                span_1b.id,
+            )
+        ]
+        == "span_1b extension"
+    )
+
+    assert (
+        doc.user_data[
+            (
+                "._.",
+                "span_extension",
+                span_2a.start_char + len(doc_1.text) + 1,
+                span_2a.end_char + len(doc_1.text) + 1,
+                span_2a.label,
+                span_2a.kb_id,
+                span_2a.id,
+            )
+        ]
+        == "span_2a extension"
+    )
\ No newline at end of file
diff --git a/spacy/tokens/doc.pyx b/spacy/tokens/doc.pyx
index 1259ad2a6..9a83a17d4 100644
--- a/spacy/tokens/doc.pyx
+++ b/spacy/tokens/doc.pyx
@@ -1178,13 +1178,22 @@ cdef class Doc:
 
             if "user_data" not in exclude:
                 for key, value in doc.user_data.items():
-                    if isinstance(key, tuple) and len(key) == 4 and key[0] == "._.":
-                        data_type, name, start, end = key
+                    if isinstance(key, tuple) and len(key) >= 4 and key[0] == "._.":
+                        data_type = key[0]
+                        name = key[1]
+                        start = key[2]
+                        end = key[3]
                         if start is not None or end is not None:
                             start += char_offset
                             if end is not None:
                                 end += char_offset
-                            concat_user_data[(data_type, name, start, end)] = copy.copy(value)
+                                _label = key[4]
+                                _kb_id = key[5]
+                                _span_id = key[6]
+                                concat_user_data[(data_type, name, start, end, _label, _kb_id, _span_id)] = copy.copy(value)
+                            else:
+                                concat_user_data[(data_type, name, start, end)] = copy.copy(value)
+
                         else:
                             warnings.warn(Warnings.W101.format(name=name))
                     else: