diff --git a/backend/FwLite/FwDataMiniLcmBridge/Api/FwDataMiniLcmApi.cs b/backend/FwLite/FwDataMiniLcmBridge/Api/FwDataMiniLcmApi.cs
index a3178a4bf..e1baecf5a 100644
--- a/backend/FwLite/FwDataMiniLcmBridge/Api/FwDataMiniLcmApi.cs
+++ b/backend/FwLite/FwDataMiniLcmBridge/Api/FwDataMiniLcmApi.cs
@@ -879,8 +879,10 @@ internal void CreateSense(ILexEntry lexEntry, Sense sense, BetweenPosition? betw
         var lexSense = LexSenseFactory.Create(sense.Id);
         InsertSense(lexEntry, lexSense, between);
         var msa = new SandboxGenericMSA() { MsaType = lexSense.GetDesiredMsaType() };
-        if (sense.PartOfSpeechId.HasValue && PartOfSpeechRepository.TryGetObject(sense.PartOfSpeechId.Value, out var pos))
+        if (sense.PartOfSpeechId.HasValue)
         {
+            var found = PartOfSpeechRepository.TryGetObject(sense.PartOfSpeechId.Value, out var pos);
+            if (!found) throw new ArgumentException($"Part of speech must exist when creating a sense (could not find GUID {sense.PartOfSpeechId.Value})");
             msa.MainPOS = pos;
         }
         lexSense.SandboxMSA = msa;
diff --git a/backend/FwLite/LcmCrdt/CrdtMiniLcmApi.cs b/backend/FwLite/LcmCrdt/CrdtMiniLcmApi.cs
index 22769bb61..30d9701b2 100644
--- a/backend/FwLite/LcmCrdt/CrdtMiniLcmApi.cs
+++ b/backend/FwLite/LcmCrdt/CrdtMiniLcmApi.cs
@@ -483,6 +483,9 @@ public async Task<Sense> CreateSense(Guid entryId, Sense sense, BetweenPosition?
         if (sense.Order != default) // we don't anticipate this being necessary, so we'll be strict for now
             throw new InvalidOperationException("Order should not be provided when creating a sense");
 
+        if (sense.PartOfSpeechId.HasValue && await GetPartOfSpeech(sense.PartOfSpeechId.Value) is null)
+            throw new InvalidOperationException($"Part of speech must exist when creating a sense (could not find GUID {sense.PartOfSpeechId.Value})");
+
         sense.Order = await OrderPicker.PickOrder(Senses.Where(s => s.EntryId == entryId), between);
         await dataModel.AddChanges(ClientId, await CreateSenseChanges(entryId, sense).ToArrayAsync());
         return await dataModel.GetLatest<Sense>(sense.Id) ?? throw new NullReferenceException();
diff --git a/backend/FwLite/MiniLcm.Tests/BasicApiTestsBase.cs b/backend/FwLite/MiniLcm.Tests/BasicApiTestsBase.cs
index ba95dd9be..de7ea1e76 100644
--- a/backend/FwLite/MiniLcm.Tests/BasicApiTestsBase.cs
+++ b/backend/FwLite/MiniLcm.Tests/BasicApiTestsBase.cs
@@ -359,14 +359,14 @@ public async Task CreateSense_WillCreateWithExistingDomains()
     }
 
     [Fact]
-    public async Task CreateSense_WontCreateMissingPartOfSpeech()
+    public async Task CreateSense_WillThrowExceptionWithMissingPartOfSpeech()
     {
         var senseId = Guid.NewGuid();
         var partOfSpeechId = Guid.NewGuid();
-        var createdSense = await Api.CreateSense(Entry1Id,
-            new Sense() { Id = senseId, PartOfSpeech = null, PartOfSpeechId = partOfSpeechId, });
-        createdSense.Id.Should().Be(senseId);
-        createdSense.PartOfSpeechId.Should().BeNull("because the part of speech does not exist (or was deleted)");
+        var exception = await Assert.ThrowsAsync<InvalidOperationException>(async () =>
+            await Api.CreateSense(Entry1Id, new Sense() { Id = senseId, PartOfSpeech = null, PartOfSpeechId = partOfSpeechId, })
+        );
+        exception.Should().NotBeNull("because the part of speech does not exist (or was deleted)");
     }
 
     [Fact]