diff --git a/bigtree/tree/helper.py b/bigtree/tree/helper.py
index 2cd50451..ca20d682 100644
--- a/bigtree/tree/helper.py
+++ b/bigtree/tree/helper.py
@@ -242,6 +242,7 @@ def get_tree_diff(
     other_tree: node.Node,
     only_diff: bool = True,
     attr_list: List[str] = [],
+    fallback_sep: str = "/",
 ) -> node.Node:
     """Get difference of `tree` to `other_tree`, changes are relative to `tree`.
 
@@ -333,11 +334,25 @@ def get_tree_diff(
         other_tree (Node): tree to be compared with
         only_diff (bool): indicator to show all nodes or only nodes that are different (+/-), defaults to True
         attr_list (List[str]): tree attributes to check for difference, defaults to empty list
+        fallback_sep (str): sep to fall back to if tree and other_tree has sep that clashes with symbols "+" / "-" / "~".
+            All node names in tree and other_tree should not contain this fallback_sep, defaults to "/"
 
     Returns:
         (Node)
     """
-    other_tree.sep = tree.sep
+    if tree.sep != other_tree.sep:
+        raise ValueError("`sep` must be the same for tree and other_tree")
+
+    forbidden_sep_symbols = ["+", "-", "~"]
+    if any(
+        forbidden_sep_symbol in tree.sep
+        for forbidden_sep_symbol in forbidden_sep_symbols
+    ):
+        tree = tree.copy()
+        other_tree = other_tree.copy()
+        tree.sep = fallback_sep
+        other_tree.sep = fallback_sep
+
     name_col = "name"
     path_col = "PATH"
     indicator_col = "Exists"
@@ -405,7 +420,9 @@ def get_tree_diff(
         ]
     data_both = data_both[[path_col]]
     if len(data_both):
-        tree_diff = construct.dataframe_to_tree(data_both, node_type=tree.__class__)
+        tree_diff = construct.dataframe_to_tree(
+            data_both, node_type=tree.__class__, sep=tree.sep
+        )
         # Handle tree attribute difference
         if len(path_changes_deque):
             path_changes_list = sorted(path_changes_deque, reverse=True)
diff --git a/tests/test_constants.py b/tests/test_constants.py
index c2adaa59..20b3428d 100644
--- a/tests/test_constants.py
+++ b/tests/test_constants.py
@@ -169,6 +169,7 @@ class Constants:
     ERROR_NODE_PRUNE_NOT_FOUND = (
         "Cannot find any node matching path_name ending with {prune_path}"
     )
+    ERROR_NODE_TREE_DIFF_DIFF_SEP = "`sep` must be the same for tree and other_tree"
 
     # tree/modify
     ERROR_MODIFY_PARAM_TYPE = (
diff --git a/tests/tree/test_helper.py b/tests/tree/test_helper.py
index 7f6096ce..0a1d5a85 100644
--- a/tests/tree/test_helper.py
+++ b/tests/tree/test_helper.py
@@ -236,10 +236,27 @@ def test_tree_diff(tree_node):
         assert_print_statement(export.print_tree, expected_str, tree=tree_only_diff)
 
     @staticmethod
-    def test_tree_diff_diff_sep(tree_node):
+    def test_tree_diff_diff_sep_error(tree_node):
         other_tree_node = helper.prune_tree(tree_node, "a/c")
-        _ = node.Node("d", parent=other_tree_node)
         other_tree_node.sep = "-"
+        with pytest.raises(ValueError) as exc_info:
+            helper.get_tree_diff(tree_node, other_tree_node)
+        assert str(exc_info.value) == Constants.ERROR_NODE_TREE_DIFF_DIFF_SEP
+
+    @staticmethod
+    def test_tree_diff_sep_clash_with_node_name_error(tree_node):
+        other_tree_node = helper.prune_tree(tree_node, "a/c")
+        _ = node.Node("/d", parent=other_tree_node)
+        with pytest.raises(exceptions.TreeError) as exc_info:
+            helper.get_tree_diff(tree_node, other_tree_node)
+        assert str(exc_info.value) == Constants.ERROR_NODE_NAME
+
+    @staticmethod
+    def test_tree_diff_sep_clash_with_node_name(tree_node):
+        other_tree_node = helper.prune_tree(tree_node, "a/c")
+        _ = node.Node("/d", parent=other_tree_node)
+        tree_node.sep = "."
+        other_tree_node.sep = "."
         tree_only_diff = helper.get_tree_diff(tree_node, other_tree_node)
         expected_str = (
             "a\n"
@@ -248,10 +265,29 @@ def test_tree_diff_diff_sep(tree_node):
             "│   └── e (-)\n"
             "│       ├── g (-)\n"
             "│       └── h (-)\n"
-            "└── d (+)\n"
+            "└── /d (+)\n"
         )
         assert_print_statement(export.print_tree, expected_str, tree=tree_only_diff)
 
+    @staticmethod
+    def test_tree_diff_forbidden_sep(tree_node):
+        other_tree_node = helper.prune_tree(tree_node, "a/c")
+        _ = node.Node("d", parent=other_tree_node)
+        for symbol in [".", "-", "+", "~"]:
+            tree_node.sep = symbol
+            other_tree_node.sep = symbol
+            tree_only_diff = helper.get_tree_diff(tree_node, other_tree_node)
+            expected_str = (
+                "a\n"
+                "├── b (-)\n"
+                "│   ├── d (-)\n"
+                "│   └── e (-)\n"
+                "│       ├── g (-)\n"
+                "│       └── h (-)\n"
+                "└── d (+)\n"
+            )
+            assert_print_statement(export.print_tree, expected_str, tree=tree_only_diff)
+
     @staticmethod
     def test_tree_diff_all_diff(tree_node):
         other_tree_node = helper.prune_tree(tree_node, "a/c")