diff --git a/src/py_avro_schema/_schemas.py b/src/py_avro_schema/_schemas.py
index 2d6a5f4..5690ba3 100644
--- a/src/py_avro_schema/_schemas.py
+++ b/src/py_avro_schema/_schemas.py
@@ -484,8 +484,13 @@ def _size(cls, py_type: Type) -> Tuple[int, int]:
 
     @staticmethod
     def _validate_size_tuple(tuple_: Tuple) -> bool:
-        """Checks whether a given tuple is a tuple of 2 integers (precision, scale)"""
-        return len(tuple_) == 2 and all(isinstance(item, int) for item in tuple_)
+        """
+        Checks whether a given tuple is a tuple of (precision, scale)
+
+        Must be integers.
+        Scale must not be greater than precision
+        """
+        return len(tuple_) == 2 and all(isinstance(item, int) for item in tuple_) and tuple_[0] >= tuple_[1]
 
     def data(self, names: NamesType) -> JSONObj:
         """Return the schema data"""
diff --git a/tests/test_logicals.py b/tests/test_logicals.py
index ea60353..b8f589a 100644
--- a/tests/test_logicals.py
+++ b/tests/test_logicals.py
@@ -112,40 +112,28 @@ def test_annotated_decimal_neg_scale():
     assert_schema(py_type, expected)
 
 
-def test_annotated_decimal_bad_no_tuple():
+def test_annotated_decimal_scale_too_big():
+    py_type = Annotated[decimal.Decimal, (5, 6)]
+    with pytest.raises(pas.TypeNotSupportedError):
+        assert_schema(py_type, {})
+
+
+def test_annotated_decimal_no_tuple():
     py_type = Annotated[decimal.Decimal, ...]
-    expected = {
-        "type": "bytes",
-        "logicalType": "decimal",
-        "precision": 5,
-        "scale": 2,
-    }
     with pytest.raises(pas.TypeNotSupportedError):
-        assert_schema(py_type, expected)
+        assert_schema(py_type, {})
 
 
 def test_annotated_decimal_tuple_wrong_length():
     py_type = Annotated[decimal.Decimal, (3, 2, 1)]
-    expected = {
-        "type": "bytes",
-        "logicalType": "decimal",
-        "precision": 5,
-        "scale": 2,
-    }
     with pytest.raises(pas.TypeNotSupportedError):
-        assert_schema(py_type, expected)
+        assert_schema(py_type, {})
 
 
 def test_annotated_decimal_tuple_wrong_type():
     py_type = Annotated[decimal.Decimal, ("a", 1)]
-    expected = {
-        "type": "bytes",
-        "logicalType": "decimal",
-        "precision": 5,
-        "scale": 2,
-    }
     with pytest.raises(pas.TypeNotSupportedError):
-        assert_schema(py_type, expected)
+        assert_schema(py_type, {})
 
 
 def test_multiple_decimals():