diff --git a/indexing-service/src/main/java/io/druid/indexing/common/task/IndexTask.java b/indexing-service/src/main/java/io/druid/indexing/common/task/IndexTask.java
index 9326279e8e5..1565871fb49 100644
--- a/indexing-service/src/main/java/io/druid/indexing/common/task/IndexTask.java
+++ b/indexing-service/src/main/java/io/druid/indexing/common/task/IndexTask.java
@@ -609,7 +609,6 @@ public class IndexTask extends AbstractTask
   @JsonTypeName("index")
   public static class IndexTuningConfig implements TuningConfig, AppenderatorConfig
   {
-    private static final int DEFAULT_TARGET_PARTITION_SIZE = 5000000;
     private static final int DEFAULT_MAX_ROWS_IN_MEMORY = 75000;
     private static final IndexSpec DEFAULT_INDEX_SPEC = new IndexSpec();
     private static final int DEFAULT_MAX_PENDING_PERSISTS = 0;
@@ -617,6 +616,8 @@ public class IndexTask extends AbstractTask
     private static final boolean DEFAULT_FORCE_EXTENDABLE_SHARD_SPECS = false;
     private static final boolean DEFAULT_REPORT_PARSE_EXCEPTIONS = false;
 
+    static final int DEFAULT_TARGET_PARTITION_SIZE = 5000000;
+
     private final Integer targetPartitionSize;
     private final int maxRowsInMemory;
     private final Integer numShards;
@@ -666,15 +667,17 @@ public class IndexTask extends AbstractTask
     )
     {
       Preconditions.checkArgument(
-          targetPartitionSize == null || targetPartitionSize == -1 || numShards == null,
+          targetPartitionSize == null || targetPartitionSize.equals(-1) || numShards == null || numShards.equals(-1),
           "targetPartitionSize and numShards cannot both be set"
       );
 
-      this.targetPartitionSize = numShards != null
+      this.targetPartitionSize = numShards != null && !numShards.equals(-1)
                                  ? null
-                                 : (targetPartitionSize == null ? DEFAULT_TARGET_PARTITION_SIZE : targetPartitionSize);
+                                 : (targetPartitionSize == null || targetPartitionSize.equals(-1)
+                                    ? DEFAULT_TARGET_PARTITION_SIZE
+                                    : targetPartitionSize);
       this.maxRowsInMemory = maxRowsInMemory == null ? DEFAULT_MAX_ROWS_IN_MEMORY : maxRowsInMemory;
-      this.numShards = numShards;
+      this.numShards = numShards == null || numShards.equals(-1) ? null : numShards;
       this.indexSpec = indexSpec == null ? DEFAULT_INDEX_SPEC : indexSpec;
       this.maxPendingPersists = maxPendingPersists == null ? DEFAULT_MAX_PENDING_PERSISTS : maxPendingPersists;
       this.buildV9Directly = buildV9Directly == null ? DEFAULT_BUILD_V9_DIRECTLY : buildV9Directly;
diff --git a/indexing-service/src/test/java/io/druid/indexing/common/task/TaskSerdeTest.java b/indexing-service/src/test/java/io/druid/indexing/common/task/TaskSerdeTest.java
index 48d283cd98d..0bc64d457d9 100644
--- a/indexing-service/src/test/java/io/druid/indexing/common/task/TaskSerdeTest.java
+++ b/indexing-service/src/test/java/io/druid/indexing/common/task/TaskSerdeTest.java
@@ -137,6 +137,25 @@ public class TaskSerdeTest
 
     Assert.assertEquals(null, tuningConfig.getTargetPartitionSize());
     Assert.assertEquals(10, (int) tuningConfig.getNumShards());
+
+    tuningConfig = jsonMapper.readValue(
+        "{\"type\":\"index\", \"targetPartitionSize\":10, \"numShards\":-1}",
+        IndexTask.IndexTuningConfig.class
+    );
+
+    Assert.assertEquals(null, tuningConfig.getNumShards());
+    Assert.assertEquals(10, (int) tuningConfig.getTargetPartitionSize());
+
+    tuningConfig = jsonMapper.readValue(
+        "{\"type\":\"index\", \"targetPartitionSize\":-1, \"numShards\":-1}",
+        IndexTask.IndexTuningConfig.class
+    );
+
+    Assert.assertEquals(null, tuningConfig.getNumShards());
+    Assert.assertEquals(
+        IndexTask.IndexTuningConfig.DEFAULT_TARGET_PARTITION_SIZE,
+        (int) tuningConfig.getTargetPartitionSize()
+    );
   }
 
   @Test