diff --git a/src/SIL.Machine.AspNetCore/Services/ServalTranslationEngineServiceV1.cs b/src/SIL.Machine.AspNetCore/Services/ServalTranslationEngineServiceV1.cs
index e93474509..8fbcdee20 100644
--- a/src/SIL.Machine.AspNetCore/Services/ServalTranslationEngineServiceV1.cs
+++ b/src/SIL.Machine.AspNetCore/Services/ServalTranslationEngineServiceV1.cs
@@ -77,7 +77,14 @@ public override async Task<Empty> StartBuild(StartBuildRequest request, ServerCa
     {
         ITranslationEngineService engineService = GetEngineService(request.EngineType);
         Models.Corpus[] corpora = request.Corpora.Select(Map).ToArray();
-        await engineService.StartBuildAsync(request.EngineId, request.BuildId, corpora, context.CancellationToken);
+        try
+        {
+            await engineService.StartBuildAsync(request.EngineId, request.BuildId, corpora, context.CancellationToken);
+        }
+        catch (InvalidOperationException e)
+        {
+            throw new RpcException(new Status(StatusCode.Aborted, e.Message));
+        }
         return Empty;
     }
 
diff --git a/src/SIL.Machine.AspNetCore/Services/TranslationEngineServiceBase.cs b/src/SIL.Machine.AspNetCore/Services/TranslationEngineServiceBase.cs
index 62bf488a4..4280b6c3a 100644
--- a/src/SIL.Machine.AspNetCore/Services/TranslationEngineServiceBase.cs
+++ b/src/SIL.Machine.AspNetCore/Services/TranslationEngineServiceBase.cs
@@ -122,19 +122,12 @@ CancellationToken cancellationToken
         // If there is a pending job, then no need to start a new one.
         if (
             await Engines.ExistsAsync(
-                e => e.EngineId == engineId && e.BuildState == BuildState.Pending,
+                e =>
+                    e.EngineId == engineId && (e.BuildState == BuildState.Pending || e.BuildState == BuildState.Active),
                 cancellationToken
             )
         )
-            return;
-
-        // cancel the existing build before starting a new build
-        string? curBuildId = await CancelBuildInternalAsync(engineId, cancellationToken);
-        if (curBuildId is not null)
-        {
-            if (!await WaitForBuildToFinishAsync(engineId, curBuildId, CancellationToken.None))
-                throw new InvalidOperationException("Unable to cancel current build.");
-        }
+            throw new InvalidOperationException("Engine is already building or pending.");
 
         // Schedule the job to occur way in the future, just so we can get the job id.
         string jobId = _jobClient.Schedule(GetJobExpression(engineId, buildId, corpora), TimeSpan.FromDays(10000));