diff --git a/e2e-tests/src/tests/bindings.test.ts b/e2e-tests/src/tests/bindings.test.ts
index 8bf55c4641..47bb1a9a20 100644
--- a/e2e-tests/src/tests/bindings.test.ts
+++ b/e2e-tests/src/tests/bindings.test.ts
@@ -182,6 +182,20 @@ test.describe('Merlin Bindings', () => {
     expect(response.status()).toEqual(404);
     expect((await response.json()).message).toEqual('no such plan');
 
+    // Returns a 404 if the SimulationDataset id is invalid
+    // message is "input mismatch exception"
+    response = await request.post(`${urls.MERLIN_URL}/constraintViolations`, {
+      data: {
+        action: {name: "check_constraints"},
+        input: {planId: plan_id, simulationDatasetId: -1},
+        request_query: "",
+        session_variables: admin.session}});
+    expect(response.status()).toEqual(404);
+    expect((await response.json())).toEqual({
+      message: "input mismatch exception",
+      cause: "simulation dataset with id `-1` does not exist"
+    });
+
     // Returns a 403 if unauthorized
     response = await request.post(`${urls.MERLIN_URL}/constraintViolations`, {
       data: {
@@ -218,7 +232,7 @@ test.describe('Merlin Bindings', () => {
         session_variables: admin.session}});
     expect(response.status()).toEqual(404);
     expect((await response.json())).toEqual({
-      message: "input mismatch exception",
+      message: "simulation dataset mismatch exception",
       cause: "Simulation Dataset with id `" + invalidSimDatasetId + "` does not belong to Plan with id `"+plan_id+"`"
     });
 
diff --git a/merlin-server/src/main/java/gov/nasa/jpl/aerie/merlin/server/http/ResponseSerializers.java b/merlin-server/src/main/java/gov/nasa/jpl/aerie/merlin/server/http/ResponseSerializers.java
index 5a66e90e69..185b5f3143 100644
--- a/merlin-server/src/main/java/gov/nasa/jpl/aerie/merlin/server/http/ResponseSerializers.java
+++ b/merlin-server/src/main/java/gov/nasa/jpl/aerie/merlin/server/http/ResponseSerializers.java
@@ -471,7 +471,7 @@ public static JsonValue serializeInputMismatchException(final InputMismatchExcep
 
   public static JsonValue serializeSimulationDatasetMismatchException(final SimulationDatasetMismatchException ex){
      return Json.createObjectBuilder()
-               .add("message", "input mismatch exception")
+               .add("message", "simulation dataset mismatch exception")
                .add("cause", ex.getMessage())
                .build();
   }
diff --git a/merlin-server/src/main/java/gov/nasa/jpl/aerie/merlin/server/services/ConstraintAction.java b/merlin-server/src/main/java/gov/nasa/jpl/aerie/merlin/server/services/ConstraintAction.java
index cfffe041e4..fa14d3fd5a 100644
--- a/merlin-server/src/main/java/gov/nasa/jpl/aerie/merlin/server/services/ConstraintAction.java
+++ b/merlin-server/src/main/java/gov/nasa/jpl/aerie/merlin/server/services/ConstraintAction.java
@@ -51,11 +51,18 @@ public List<ConstraintResult> getViolations(final PlanId planId, final Optional<
       throws NoSuchPlanException, MissionModelService.NoSuchMissionModelException, SimulationDatasetMismatchException {
     final var plan = this.planService.getPlanForValidation(planId);
     final Optional<SimulationResultsHandle> resultsHandle$;
+    final SimulationDatasetId simDatasetId;
     if (simulationDatasetId.isPresent()) {
       resultsHandle$ = this.simulationService.get(planId, simulationDatasetId.get());
+      simDatasetId = resultsHandle$
+        .map(SimulationResultsHandle::getSimulationDatasetId)
+        .orElseThrow(() -> new InputMismatchException("simulation dataset with id `" + simulationDatasetId.get().id() + "` does not exist"));
     } else {
       final var revisionData = this.planService.getPlanRevisionData(planId);
       resultsHandle$ = this.simulationService.get(planId, revisionData);
+      simDatasetId = resultsHandle$
+        .map(SimulationResultsHandle::getSimulationDatasetId)
+        .orElseThrow(() -> new InputMismatchException("no simulation datasets found for plan id " + planId.id()));
     }
 
 
@@ -68,9 +75,6 @@ public List<ConstraintResult> getViolations(final PlanId planId, final Optional<
       throw new RuntimeException("Assumption falsified -- mission model for existing plan does not exist");
     }
 
-    final var simDatasetId = resultsHandle$
-        .map(SimulationResultsHandle::getSimulationDatasetId)
-        .orElseThrow(() -> new InputMismatchException("no simulation datasets found for plan id " + planId.id()));
     final var violations = new HashMap<Long, ConstraintResult>();
 
     final var validConstraintRuns = this.constraintService.getValidConstraintRuns(constraintCode.values().stream().toList(), simDatasetId);