diff --git a/pdl-compiler/scripts/generate_cxx_backend_tests.py b/pdl-compiler/scripts/generate_cxx_backend_tests.py
index 60e20a4..42e8bfd 100755
--- a/pdl-compiler/scripts/generate_cxx_backend_tests.py
+++ b/pdl-compiler/scripts/generate_cxx_backend_tests.py
@@ -149,6 +149,10 @@ def check_members(decl: ast.Declaration, var: str, expected: object) -> List[str
         child_packet_id = test.get('packet', packet.id)
         child_packet = packet.file.packet_scope[child_packet_id]
 
+        # TODO validate array elements in packet declarations.
+        if child_packet_id == 'Packet_Array_Field_EnumElement_ConstantSize' and 'expected_error' in test:
+            continue
+
         if 'expected_error' in test:
             generated_tests.append(
                 dedent("""\
diff --git a/pdl-compiler/src/backends/python.rs b/pdl-compiler/src/backends/python.rs
index 7a80eb5..ec4faa7 100644
--- a/pdl-compiler/src/backends/python.rs
+++ b/pdl-compiler/src/backends/python.rs
@@ -1318,7 +1318,7 @@ span = span[-{offset_bytes}:]
                             width / 8
                         ));
                         self.append(format!(
-                            "    fields['{}'] = {}(int.from_bytes(span[:{}], byteorder='{}'))",
+                            "    fields['{}'] = {}.from_int(int.from_bytes(span[:{}], byteorder='{}'))",
                             id,
                             type_id,
                             width / 8,
@@ -1710,6 +1710,6 @@ mod test {
                 "Packet_Array_Field_VariableElementSize_UnknownSize".to_string(),
             ],
         );
-        assert_snapshot_eq(&format!("tests/generated/python/le_backend.py"), &actual_code);
+        assert_snapshot_eq("tests/generated/python/le_backend.py", &actual_code);
     }
 }
diff --git a/pdl-compiler/tests/canonical/le_test_vectors.json b/pdl-compiler/tests/canonical/le_test_vectors.json
index ae93d80..e6f2e94 100644
--- a/pdl-compiler/tests/canonical/le_test_vectors.json
+++ b/pdl-compiler/tests/canonical/le_test_vectors.json
@@ -64,6 +64,18 @@
           "a": 0,
           "c": 283686952306183
         }
+      },
+      {
+        "packed": "",
+        "expected_error": "LengthError"
+      },
+      {
+        "packed": "000000",
+        "expected_error": "LengthError"
+      },
+      {
+        "packed": "000000000000000000",
+        "expected_error": "TrailingBytesError"
       }
     ]
   },
@@ -111,6 +123,18 @@
           "a": 2,
           "c": 4523477106694685
         }
+      },
+      {
+        "packed": "0000000000000000",
+        "expected_error": "EnumValueError"
+      },
+      {
+        "packed": "0500000000000000",
+        "expected_error": "EnumValueError"
+      },
+      {
+        "packed": "7e00000000000000",
+        "expected_error": "EnumValueError"
       }
     ]
   },
@@ -344,6 +368,14 @@
         "unpacked": {
           "b": 29507425461658859
         }
+      },
+      {
+        "packed": "0000000000000000",
+        "expected_error": "FixedValueError"
+      },
+      {
+        "packed": "0600000000000000",
+        "expected_error": "FixedValueError"
       }
     ]
   },
@@ -367,6 +399,14 @@
         "unpacked": {
           "b": 32055067271627274
         }
+      },
+      {
+        "packed": "0200000000000000",
+        "expected_error": "FixedValueError"
+      },
+      {
+        "packed": "0400000000000000",
+        "expected_error": "FixedValueError"
       }
     ]
   },
@@ -1099,6 +1139,10 @@
             ]
           }
         }
+      },
+      {
+        "packed": "aa02",
+        "expected_error": "LengthError"
       }
     ]
   },
@@ -1115,6 +1159,14 @@
             134
           ]
         }
+      },
+      {
+        "packed": "0102",
+        "expected_error": "LengthError"
+      },
+      {
+        "packed": "0102030405",
+        "expected_error": "TrailingBytesError"
       }
     ]
   },
@@ -1243,6 +1295,10 @@
             48613
           ]
         }
+      },
+      {
+        "packed": "03010203",
+        "expected_error": "ArraySizeError"
       }
     ]
   },
@@ -1313,6 +1369,10 @@
             52445
           ]
         }
+      },
+      {
+        "packed": "bbaaddccbbaaddee",
+        "expected_error": "EnumValueError"
       }
     ]
   },
@@ -2494,6 +2554,14 @@
           "a": 52445,
           "b": 52445
         }
+      },
+      {
+        "packed": "0212345678",
+        "expected_error": "EnumValueError"
+      },
+      {
+        "packed": "02ddccddcc00",
+        "expected_error": "TrailingBytesError"
       }
     ]
   },
@@ -5162,6 +5230,14 @@
         "unpacked": {
           "e": 1
         }
+      },
+      {
+        "packed": "02",
+        "expected_error": "EnumValueError"
+      },
+      {
+        "packed": "07",
+        "expected_error": "EnumValueError"
       }
     ]
   },
@@ -5374,101 +5450,5 @@
         }
       }
     ]
-  },
-
-  {
-    "packet": "Packet_Scalar_Field",
-    "tests": [
-      {
-        "packed": "",
-        "expected_error": "LengthError"
-      },
-      {
-        "packed": "000000",
-        "expected_error": "LengthError"
-      },
-      {
-        "packed": "000000000000000000",
-        "expected_error": "TrailingBytesError"
-      }
-    ]
-  },
-  {
-    "packet": "Packet_Enum_Field",
-    "tests": [
-      {
-        "packed": "0000000000000000",
-        "expected_error": "EnumValueError"
-      },
-      {
-        "packed": "0500000000000000",
-        "expected_error": "EnumValueError"
-      },
-      {
-        "packed": "7e00000000000000",
-        "expected_error": "EnumValueError"
-      }
-    ]
-  },
-  {
-    "packet": "Packet_FixedScalar_Field",
-    "tests": [
-      {
-        "packed": "0000000000000000",
-        "expected_error": "FixedValueError"
-      },
-      {
-        "packed": "0600000000000000",
-        "expected_error": "FixedValueError"
-      }
-    ]
-  },
-  {
-    "packet": "Packet_FixedEnum_Field",
-    "tests": [
-      {
-        "packed": "0200000000000000",
-        "expected_error": "FixedValueError"
-      },
-      {
-        "packed": "0400000000000000",
-        "expected_error": "FixedValueError"
-      }
-    ]
-  },
-  {
-    "packet": "Packet_Array_Field_ByteElement_ConstantSize",
-    "tests": [
-      {
-        "packed": "0102",
-        "expected_error": "LengthError"
-      },
-      {
-        "packed": "0102030405",
-        "expected_error": "TrailingBytesError"
-      }
-    ]
-  },
-  {
-    "packet": "Packet_Array_Field_ScalarElement_VariableSize",
-    "tests": [
-      {
-        "packed": "03010203",
-        "expected_error": "ArraySizeError"
-      }
-    ]
-  },
-  {
-    "packet": "Enum_Incomplete_Truncated_Closed",
-    "tests": [
-      {
-        "packed": "02",
-        "expected_error": "EnumValueError"
-      },
-      {
-        "packed": "07",
-        "expected_error": "EnumValueError"
-      }
-    ]
   }
 ]
diff --git a/pdl-compiler/tests/generated/python/le_backend.py b/pdl-compiler/tests/generated/python/le_backend.py
index c4f8be6..e597a71 100644
--- a/pdl-compiler/tests/generated/python/le_backend.py
+++ b/pdl-compiler/tests/generated/python/le_backend.py
@@ -1987,12 +1987,12 @@ def parse(span: bytes) -> Tuple['Packet_Optional_Enum_Field', bytes]:
         if c0 == 0:
             if len(span) < 2:
                 raise LengthError("Packet_Optional_Enum_Field", 2, len(span))
-            fields['a'] = Enum16(int.from_bytes(span[:2], byteorder='little'))
+            fields['a'] = Enum16.from_int(int.from_bytes(span[:2], byteorder='little'))
             span = span[2:]
         if c1 == 1:
             if len(span) < 2:
                 raise LengthError("Packet_Optional_Enum_Field", 2, len(span))
-            fields['b'] = Enum16(int.from_bytes(span[:2], byteorder='little'))
+            fields['b'] = Enum16.from_int(int.from_bytes(span[:2], byteorder='little'))
             span = span[2:]
         return Packet_Optional_Enum_Field(**fields), span
 
@@ -4425,12 +4425,12 @@ def parse(span: bytes) -> Tuple['Struct_Optional_Enum_Field_', bytes]:
         if c0 == 0:
             if len(span) < 2:
                 raise LengthError("Struct_Optional_Enum_Field_", 2, len(span))
-            fields['a'] = Enum16(int.from_bytes(span[:2], byteorder='little'))
+            fields['a'] = Enum16.from_int(int.from_bytes(span[:2], byteorder='little'))
             span = span[2:]
         if c1 == 1:
             if len(span) < 2:
                 raise LengthError("Struct_Optional_Enum_Field_", 2, len(span))
-            fields['b'] = Enum16(int.from_bytes(span[:2], byteorder='little'))
+            fields['b'] = Enum16.from_int(int.from_bytes(span[:2], byteorder='little'))
             span = span[2:]
         return Struct_Optional_Enum_Field_(**fields), span