diff --git a/amaranth/lib/data.py b/amaranth/lib/data.py
index 3167536..4bd010d 100644
--- a/amaranth/lib/data.py
+++ b/amaranth/lib/data.py
@@ -425,7 +425,7 @@ class _AggregateMeta(ShapeCastable, type):
         else:
             # This is a class that has a base class with a layout and annotations. Such a class
             # is not well-formed.
-            raise TypeError("Aggregate class '{}' must either inherits or specify a layout, "
+            raise TypeError("Aggregate class '{}' must either inherit or specify a layout, "
                             "not both"
                             .format(name))
 
diff --git a/tests/test_lib_data.py b/tests/test_lib_data.py
index 2ab0092..6ed9693 100644
--- a/tests/test_lib_data.py
+++ b/tests/test_lib_data.py
@@ -635,7 +635,7 @@ class StructTestCase(FHDLTestCase):
             a: 1
 
         with self.assertRaisesRegex(TypeError,
-                r"^Aggregate class 'Sd' must either inherits or specify a layout, not both$"):
+                r"^Aggregate class 'Sd' must either inherit or specify a layout, not both$"):
             class Sd(Sb):
                 b: 1