diff --git a/protobuf-codegen/src/gen/field/mod.rs b/protobuf-codegen/src/gen/field/mod.rs
index 79a16e05e..54e17b843 100644
--- a/protobuf-codegen/src/gen/field/mod.rs
+++ b/protobuf-codegen/src/gen/field/mod.rs
@@ -185,40 +185,43 @@ impl<'a> FieldGen<'a> {
             }
             RuntimeFieldType::Repeated(..) => {
                 let elem = field_elem(&field, root_scope, &customize);
-
-                FieldKind::Repeated(RepeatedField {
-                    elem,
-                    packed: field
-                        .field
-                        .proto()
-                        .options
-                        .get_or_default()
-                        .packed
-                        .unwrap_or(match field.message.scope.file_scope.syntax() {
-                            Syntax::Proto2 => false,
-                            // in proto3, repeated primitive types are packed by default
-                            Syntax::Proto3 => match field.field.proto().type_() {
-                                Type::TYPE_DOUBLE
-                                | Type::TYPE_FLOAT
-                                | Type::TYPE_INT64
-                                | Type::TYPE_UINT64
-                                | Type::TYPE_INT32
-                                | Type::TYPE_FIXED64
-                                | Type::TYPE_FIXED32
-                                | Type::TYPE_BOOL
-                                | Type::TYPE_UINT32
-                                | Type::TYPE_SFIXED32
-                                | Type::TYPE_SFIXED64
-                                | Type::TYPE_SINT32
-                                | Type::TYPE_SINT64 => true,
-                                Type::TYPE_STRING
-                                | Type::TYPE_GROUP
-                                | Type::TYPE_MESSAGE
-                                | Type::TYPE_BYTES
-                                | Type::TYPE_ENUM => false,
-                            },
-                        }),
-                })
+                let primitive = match field.field.proto().type_() {
+                    Type::TYPE_DOUBLE
+                    | Type::TYPE_FLOAT
+                    | Type::TYPE_INT64
+                    | Type::TYPE_UINT64
+                    | Type::TYPE_INT32
+                    | Type::TYPE_FIXED64
+                    | Type::TYPE_FIXED32
+                    | Type::TYPE_BOOL
+                    | Type::TYPE_UINT32
+                    | Type::TYPE_SFIXED32
+                    | Type::TYPE_SFIXED64
+                    | Type::TYPE_SINT32
+                    | Type::TYPE_SINT64 => true,
+                    Type::TYPE_STRING
+                    | Type::TYPE_GROUP
+                    | Type::TYPE_MESSAGE
+                    | Type::TYPE_BYTES
+                    | Type::TYPE_ENUM => false,
+                };
+                let packed = field
+                    .field
+                    .proto()
+                    .options
+                    .get_or_default()
+                    .packed
+                    .unwrap_or(match field.message.scope.file_scope.syntax() {
+                        Syntax::Proto2 => false,
+                        // in proto3, repeated primitive types are packed by default
+                        Syntax::Proto3 => primitive,
+                    });
+                if packed && !primitive {
+                    anyhow::bail!(
+                        "[packed = true] can only be specified for repeated primitive fields"
+                    );
+                }
+                FieldKind::Repeated(RepeatedField { elem, packed })
             }
             RuntimeFieldType::Singular(..) => {
                 let elem = field_elem(&field, root_scope, &customize);