diff --git a/sentry_sdk/scope.py b/sentry_sdk/scope.py
index bb45143c48..463f48fac6 100644
--- a/sentry_sdk/scope.py
+++ b/sentry_sdk/scope.py
@@ -230,7 +230,7 @@ def __copy__(self):
         rv._name = self._name
         rv._fingerprint = self._fingerprint
         rv._transaction = self._transaction
-        rv._transaction_info = dict(self._transaction_info)
+        rv._transaction_info = copy(self._transaction_info)
         rv._user = self._user
 
         rv._tags = dict(self._tags)
@@ -669,7 +669,7 @@ def clear(self):
         self._level = None  # type: Optional[LogLevelStr]
         self._fingerprint = None  # type: Optional[List[str]]
         self._transaction = None  # type: Optional[str]
-        self._transaction_info = {}  # type: MutableMapping[str, str]
+        self._transaction_info = None  # type: Optional[MutableMapping[str, str]]
         self._user = None  # type: Optional[Dict[str, Any]]
 
         self._tags = {}  # type: Dict[str, Any]
@@ -778,7 +778,10 @@ def set_transaction_name(self, name, source=None):
                 self._span.containing_transaction.source = source
 
         if source:
-            self._transaction_info["source"] = source
+            if self._transaction_info is None:
+                self._transaction_info = {"source": source}
+            else:
+                self._transaction_info["source"] = source
 
     @_attr_setter
     def user(self, value):
@@ -811,7 +814,10 @@ def span(self, span):
             if transaction.name:
                 self._transaction = transaction.name
                 if transaction.source:
-                    self._transaction_info["source"] = transaction.source
+                    if self._transaction_info is None:
+                        self._transaction_info = {"source": transaction.source}
+                    else:
+                        self._transaction_info["source"] = transaction.source
 
     @property
     def profile(self):
@@ -1497,7 +1503,10 @@ def update_from_scope(self, scope):
         if scope._transaction is not None:
             self._transaction = scope._transaction
         if scope._transaction_info is not None:
-            self._transaction_info.update(scope._transaction_info)
+            if self._transaction_info is None:
+                self._transaction_info = scope._transaction_info
+            else:
+                self._transaction_info.update(scope._transaction_info)
         if scope._user is not None:
             self._user = scope._user
         if scope._tags:
diff --git a/tests/test_scope.py b/tests/test_scope.py
index a03eb07a99..f41fdb70dd 100644
--- a/tests/test_scope.py
+++ b/tests/test_scope.py
@@ -883,3 +883,11 @@ def test_last_event_id_cleared(sentry_init):
     Scope.get_isolation_scope().clear()
 
     assert Scope.last_event_id() is None, "last_event_id should be cleared"
+
+
+def test_transaction_info_default_is_none(sentry_init):
+    sentry_init(traces_sample_rate=1.0)
+
+    scope = sentry_sdk.get_current_scope()
+
+    assert scope._transaction_info is None