diff --git a/app.js b/app.js
index ac3b1683..ff9e2877 100644
--- a/app.js
+++ b/app.js
@@ -6,6 +6,7 @@ const loadConfig = require('./lib/load-config')
 const { preflightCheck } = require('./lib/preflight_check')
 const { loadNyplCoreData } = require('./lib/load_nypl_core')
 const handleError = require('./lib/handle-error')
+const { NotFoundError } = require('./lib/errors')
 
 const swaggerDocs = require('./swagger.v1.1.x.json')
 
@@ -60,6 +61,10 @@ app.init = async () => {
     res.send(swaggerDocs)
   })
 
+  app.use((req, res, next) => {
+    next(new NotFoundError(`Route ${req.originalUrl} not found`))
+  })
+
   app.use((err, req, res, next) => {
     handleError(err, req, res, next, app.logger)
   })
diff --git a/lib/jsonld_serializers.js b/lib/jsonld_serializers.js
index 79e0d154..5ed90a0e 100644
--- a/lib/jsonld_serializers.js
+++ b/lib/jsonld_serializers.js
@@ -398,7 +398,7 @@ class ItemResourceSerializer extends JsonLdItemSerializer {
     // Ensure identifiers array exists:
     item.identifier = item.identifier || []
     const nyplSourceMapper = await NyplSourceMapper.instance()
-    const { id, nyplSource, type } = nyplSourceMapper.splitIdentifier(item.uri)
+    const { id, nyplSource, type } = nyplSourceMapper.splitIdentifier(item.uri) ?? {}
     if (type === 'item') {
       // Build prefix nyplSource as camel case
       const sourceIdentifierPrefix = ItemResourceSerializer.sourceIdentifierPrefixByNyplSource(nyplSource)
@@ -485,7 +485,7 @@ class AggregationsSerializer extends JsonLdListSerializer {
     if ((typeof options) === 'undefined') options = {}
 
     const items = await Promise.all(
-      Object.entries(resp.aggregations)
+      Object.entries(resp.aggregations || {})
         // Add id property to body of aggregation:
         .map(([id, agg]) => Object.assign({ id }, agg))
         .map((agg) => AggregationSerializer.serialize(agg, options))
diff --git a/lib/resources.js b/lib/resources.js
index e95de659..57532f96 100644
--- a/lib/resources.js
+++ b/lib/resources.js
@@ -114,7 +114,7 @@ module.exports = function (app, _private = null) {
 
     // Validate uri:
     const nyplSourceMapper = await NyplSourceMapper.instance()
-    const { id, nyplSource } = nyplSourceMapper.splitIdentifier(params.uri)
+    const { id, nyplSource } = nyplSourceMapper.splitIdentifier(params.uri) ?? {}
     if (!id || !nyplSource) {
       throw new errors.InvalidParameterError(`Invalid bnum: ${params.uri}`)
     }
@@ -211,9 +211,14 @@ module.exports = function (app, _private = null) {
   app.resources.annotatedMarc = async function (params, opts) {
     // Convert discovery id to nyplSource and un-prefixed id:
     const nyplSourceMapper = await NyplSourceMapper.instance()
-    const { id, nyplSource } = nyplSourceMapper.splitIdentifier(params.uri)
+    const { id, nyplSource } = nyplSourceMapper.splitIdentifier(params.uri) ?? {}
+
+    if (!id || !nyplSource) {
+      throw new errors.InvalidParameterError(`Invalid bnum: ${params.uri}`)
+    }
 
     app.logger.debug('Resources#annotatedMarc', { id, nyplSource })
+
     return makeNyplDataApiClient().get(`bibs/${nyplSource}/${id}`)
       .then((resp) => {
         // need to check that the query actually found an entry
diff --git a/test/jsonld-serializers.test.js b/test/jsonld-serializers.test.js
index 10c97848..10526662 100644
--- a/test/jsonld-serializers.test.js
+++ b/test/jsonld-serializers.test.js
@@ -3,9 +3,12 @@ const { expect } = require('chai')
 const {
   AggregationsSerializer,
   ItemResultsSerializer,
+  ItemResourceSerializer,
   ResourceSerializer
 } = require('../lib/jsonld_serializers')
 
+const NyplSourceMapper = require('research-catalog-indexer/lib/utils/nypl-source-mapper')
+
 describe('JSONLD Serializers', () => {
   describe('ResourceSerializer', () => {
     it('enables hasItemDates when numItemsTotal is above thresshold', async () => {
@@ -172,5 +175,22 @@ describe('JSONLD Serializers', () => {
         .filter((val) => !val.label)
       expect(bucketsWithoutLabels).to.have.lengthOf(0)
     })
+
+    it('defaults to empty aggregations if missing', async () => {
+      const serialized = await AggregationsSerializer.serialize({ hits: { total: 0 } })
+      expect(serialized.itemListElement).to.deep.equal([])
+      expect(serialized.totalResults).to.equal(0)
+    })
+  })
+
+  describe('ItemResourceSerializer', async () => {
+    describe('addSourceIdentifier', async () => {
+      it('makes no change if item uri has unexpected format', async () => {
+        await NyplSourceMapper.loadInstance({})
+        const fakeItem = { uri: '1234' }
+        await ItemResourceSerializer.addSourceIdentifier(fakeItem)
+        expect(fakeItem).to.deep.equal({ uri: '1234', identifier: [] })
+      })
+    })
   })
 })
diff --git a/test/resources.test.js b/test/resources.test.js
index 7ae45032..056a2926 100644
--- a/test/resources.test.js
+++ b/test/resources.test.js
@@ -410,6 +410,13 @@ describe('Resources query', function () {
           expect(data.bib.id).to.eq('11055155')
         })
     })
+
+    it('Throws InvalidParameterError for unexpected uri format', async () => {
+      return app.resources.annotatedMarc({ uri: '1234' })
+        .catch((e) => {
+          expect(e.message).to.equal('Invalid bnum: 1234')
+        })
+    })
   })
 
   describe('findByUri 4xx', () => {
@@ -604,6 +611,24 @@ describe('Resources query', function () {
     })
   })
 
+  describe('findByUri with unexpected uri format', async () => {
+    before(() => {
+      fixtures.enableEsFixtures()
+    })
+
+    after(() => {
+      fixtures.disableEsFixtures()
+    })
+
+    it('throws an InvalidParameterError', () => {
+      return app.resources.findByUri({ uri: '1234' })
+        .catch((e) => {
+          console.log('message: ', e.message)
+          expect(e.message).to.equal('Invalid bnum: 1234')
+        })
+    })
+  })
+
   describe('esRangeValue', () => {
     it('should handle a range with two values', () => {
       expect(resourcesPrivMethods.esRangeValue([123, 456])).to.deep.equal({