diff --git a/gtkblueprinttool/ast.py b/gtkblueprinttool/ast.py
index 7c1f51f..4976eee 100644
--- a/gtkblueprinttool/ast.py
+++ b/gtkblueprinttool/ast.py
@@ -51,6 +51,11 @@ class UI(AstNode):
         return gir_ctx
 
 
+    @lazy_prop
+    def objects_by_id(self):
+        return { obj.id: obj for obj in self.iterate_children_recursive() if hasattr(obj, "id") }
+
+
     @validate()
     def gir_errors(self):
         # make sure gir is loaded
@@ -66,6 +71,19 @@ class UI(AstNode):
                                self.children[Template][1].group.start)
 
 
+    @validate()
+    def unique_ids(self):
+        passed = {}
+        for obj in self.iterate_children_recursive():
+            if obj.tokens["id"] is None:
+                continue
+
+            if obj.tokens["id"] in passed:
+                token = obj.group.tokens["id"]
+                raise CompileError(f"Duplicate object ID '{obj.tokens['id']}'", token.start, token.end)
+            passed[obj.tokens["id"]] = obj
+
+
     def emit_xml(self, xml: XmlEmitter):
         xml.start_tag("interface")
         for x in self.children:
diff --git a/gtkblueprinttool/ast_utils.py b/gtkblueprinttool/ast_utils.py
index aa4803f..fc0ac72 100644
--- a/gtkblueprinttool/ast_utils.py
+++ b/gtkblueprinttool/ast_utils.py
@@ -118,6 +118,12 @@ class AstNode:
             yield from child.get_semantic_tokens()
 
 
+    def iterate_children_recursive(self) -> T.Iterator["AstNode"]:
+        yield self
+        for child in self.children:
+            yield from child.iterate_children_recursive()
+
+
 def validate(token_name=None, end_token_name=None, skip_incomplete=False):
     """ Decorator for functions that validate an AST node. Exceptions raised
     during validation are marked with range information from the tokens. Also
diff --git a/tests/sample_errors/duplicate_obj_id.blp b/tests/sample_errors/duplicate_obj_id.blp
new file mode 100644
index 0000000..6c0b660
--- /dev/null
+++ b/tests/sample_errors/duplicate_obj_id.blp
@@ -0,0 +1,4 @@
+using Gtk 4.0;
+
+Gtk.Label label {}
+Gtk.Label label {}
diff --git a/tests/sample_errors/duplicate_obj_id.err b/tests/sample_errors/duplicate_obj_id.err
new file mode 100644
index 0000000..e9c753c
--- /dev/null
+++ b/tests/sample_errors/duplicate_obj_id.err
@@ -0,0 +1 @@
+4,11,5,Duplicate object ID 'label'
diff --git a/tests/test_samples.py b/tests/test_samples.py
index 08d376e..414a88a 100644
--- a/tests/test_samples.py
+++ b/tests/test_samples.py
@@ -24,8 +24,9 @@ import traceback
 import unittest
 
 from gtkblueprinttool import tokenizer, parser
-from gtkblueprinttool.errors import PrintableError, MultipleErrors
+from gtkblueprinttool.errors import PrintableError, MultipleErrors, CompileError
 from gtkblueprinttool.tokenizer import Token, TokenType, tokenize
+from gtkblueprinttool import utils
 
 
 class TestSamples(unittest.TestCase):
@@ -54,6 +55,39 @@ class TestSamples(unittest.TestCase):
             raise AssertionError()
 
 
+    def assert_sample_error(self, name):
+        try:
+            with open((Path(__file__).parent / f"sample_errors/{name}.blp").resolve()) as f:
+                blueprint = f.read()
+            with open((Path(__file__).parent / f"sample_errors/{name}.err").resolve()) as f:
+                expected = f.read()
+
+            tokens = tokenizer.tokenize(blueprint)
+            ast, errors = parser.parse(tokens)
+
+            if errors:
+                raise errors
+            if len(ast.errors):
+                raise MultipleErrors(ast.errors)
+        except PrintableError as e:
+            def error_str(error):
+                line, col = utils.idx_to_pos(error.start, blueprint)
+                len = error.end - error.start
+                return ",".join([str(line + 1), str(col), str(len), error.message])
+
+            if isinstance(e, CompileError):
+                actual = error_str(e)
+            elif isinstance(e, MultipleErrors):
+                actual = "\n".join([error_str(error) for error in e.errors])
+            else:
+                raise AssertionError()
+
+            if actual.strip() != expected.strip():
+                diff = difflib.unified_diff(expected.splitlines(), actual.splitlines())
+                print("\n".join(diff))
+                raise AssertionError()
+
+
     def test_samples(self):
         self.assert_sample("binding")
         self.assert_sample("child_type")
@@ -66,3 +100,7 @@ class TestSamples(unittest.TestCase):
         self.assert_sample("style")
         self.assert_sample("template")
         self.assert_sample("using")
+
+
+    def test_sample_errors(self):
+        self.assert_sample_error("duplicate_obj_id")