diff --git a/sjsonnet/src/sjsonnet/Evaluator.scala b/sjsonnet/src/sjsonnet/Evaluator.scala
index 31d1cb2d..cef32e9a 100644
--- a/sjsonnet/src/sjsonnet/Evaluator.scala
+++ b/sjsonnet/src/sjsonnet/Evaluator.scala
@@ -589,12 +589,16 @@ class Evaluator(resolver: CachedResolver,
 
         visitExpr(e.key)(s) match {
           case Val.Str(_, k) =>
+            val prev_length = builder.size()
             builder.put(k, new Val.Obj.Member(false, Visibility.Normal) {
               def invoke(self: Val.Obj, sup: Val.Obj, fs: FileScope, ev: EvalScope): Val =
                 visitExpr(e.value)(
                   s.extend(newBindings, self, null)
                 )
             })
+            if (prev_length == builder.size()) {
+              Error.fail(s"Duplicate key ${k} in evaluated object comprehension.", e.pos);
+            }
           case Val.Null(_) => // do nothing
         }
       }
diff --git a/sjsonnet/test/src/sjsonnet/EvaluatorTests.scala b/sjsonnet/test/src/sjsonnet/EvaluatorTests.scala
index 9ff12b46..77bdeb32 100644
--- a/sjsonnet/test/src/sjsonnet/EvaluatorTests.scala
+++ b/sjsonnet/test/src/sjsonnet/EvaluatorTests.scala
@@ -338,6 +338,19 @@ object EvaluatorTests extends TestSuite{
     test("givenNoDuplicateFieldsInListComprehension2_expectSuccess") {
       eval("""{ ["bar_" + x]: x for x in [5,12]}""") ==> ujson.Obj("bar_5" -> 5, "bar_12" -> 12)
     }
+    test("givenDuplicateFieldsInListComprehension_expectFailure") {
+      evalErr("""{ [x]: x for x in ["A", "A"]}""") ==>
+        """sjsonnet.Error: Duplicate key A in evaluated object comprehension.
+          |at .(:1:3)""".stripMargin
+    }
+    test("givenDuplicateFieldsInIndirectListComprehension_expectFailure") {
+      evalErr(
+        """local y = { a: "A" };
+          |local z = { a: "A" };
+          |{ [x.a]: x for x in [y, z]}""".stripMargin) ==>
+        """sjsonnet.Error: Duplicate key A in evaluated object comprehension.
+          |at .(:3:3)""".stripMargin
+    }
     test("functionEqualsNull") {
       eval("""local f(x)=null; f == null""") ==> ujson.False
       eval("""local f=null; f == null""") ==> ujson.True