Swift experimental-module-manifest cannot reference enums from another module

We've found that swift modules do not work when referencing enums.
Here's a repo that reproduces the issue.

TL;DR

proto/foo/v1/foo.proto

syntax = "proto3";

package foo.v1;

import "bar/v1/bar.proto";

// Foo represents a basic entity with a single Bar field
message Foo {
  bar.v1.Bar bar = 1;
}

proto/bar/v1/bar.proto

syntax = "proto3";

package bar.v1;

// an example enum
enum Bar {
  BAR_UNSPECIFIED = 0;
  BAR_A = 1;
  BAR_B = 2;
}

wire.yaml

Foo:
  roots:
    - foo.v1.*
  dependencies:
    - Bar

Bar:
  roots:
    - bar.v1.*

❯ rm -rf swift/modules && java -jar wire-compiler-5.3.3.jar \
    --proto_path=proto/ \
    --swift_out=swift/modules \
    --experimental-module-manifest=wire.yaml
Writing .Bar declared in bar/v1/bar.proto to swift/modules/Bar (target=Swift)
Exception in thread "main" java.util.NoSuchElementException: Missing a zero value for Bar
        at com.squareup.wire.swift.SwiftGenerator.validateProto3DefaultsExist(SwiftGenerator.kt:312)
        at com.squareup.wire.swift.SwiftGenerator.generateMessage(SwiftGenerator.kt:335)
        at com.squareup.wire.swift.SwiftGenerator.generateType(SwiftGenerator.kt:269)
        at com.squareup.wire.swift.SwiftGenerator.generateTypeTo(SwiftGenerator.kt:256)
        at com.squareup.wire.swift.SwiftSchemaHandler.handle(SwiftSchemaHandler.kt:47)
        at com.squareup.wire.schema.SchemaHandler.handle(SchemaHandler.kt:152)
        at com.squareup.wire.schema.SchemaHandler.handle(SchemaHandler.kt:43)
        at com.squareup.wire.swift.SwiftSchemaHandler.handle(SwiftSchemaHandler.kt:34)
        at com.squareup.wire.schema.WireRun.execute$wire_schema(WireRun.kt:321)
        at com.squareup.wire.schema.WireRun.execute(WireRun.kt:240)
        at com.squareup.wire.WireCompiler.compile(WireCompiler.kt:228)
        at com.squareup.wire.WireCompiler$Companion.main(WireCompiler.kt:302)
        at com.squareup.wire.WireCompiler.main(WireCompiler.kt)

The same proto files generate without experimental-module-manifest.

Run the linked enum reproducer with the shown proto files, wire.yaml, and --experimental-module-manifest. Start at SwiftGenerator.kt:312 and follow the generateMessage/generateType path shown in the trace. Done means the same modules generate successfully when Foo references the enum Bar from another module, as they do without the manifest.