diff --git a/akka-distributed-data/src/main/java/akka/cluster/ddata/protobuf/msg/ReplicatedDataMessages.java b/akka-distributed-data/src/main/java/akka/cluster/ddata/protobuf/msg/ReplicatedDataMessages.java
index 1f25776e93..2cbf071334 100644
--- a/akka-distributed-data/src/main/java/akka/cluster/ddata/protobuf/msg/ReplicatedDataMessages.java
+++ b/akka-distributed-data/src/main/java/akka/cluster/ddata/protobuf/msg/ReplicatedDataMessages.java
@@ -9846,17 +9846,17 @@ public final class ReplicatedDataMessages {
       akka.protobuf.ByteString
           getStringKeyBytes();
 
-      // required .akka.cluster.ddata.OtherMessage value = 2;
+      // optional .akka.cluster.ddata.OtherMessage value = 2;
       /**
-       * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+       * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
        */
       boolean hasValue();
       /**
-       * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+       * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
        */
       akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage getValue();
       /**
-       * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+       * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
        */
       akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessageOrBuilder getValueOrBuilder();
 
@@ -10069,23 +10069,23 @@ public final class ReplicatedDataMessages {
         }
       }
 
-      // required .akka.cluster.ddata.OtherMessage value = 2;
+      // optional .akka.cluster.ddata.OtherMessage value = 2;
       public static final int VALUE_FIELD_NUMBER = 2;
       private akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage value_;
       /**
-       * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+       * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
        */
       public boolean hasValue() {
         return ((bitField0_ & 0x00000002) == 0x00000002);
       }
       /**
-       * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+       * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
        */
       public akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage getValue() {
         return value_;
       }
       /**
-       * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+       * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
        */
       public akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessageOrBuilder getValueOrBuilder() {
         return value_;
@@ -10157,13 +10157,11 @@ public final class ReplicatedDataMessages {
         byte isInitialized = memoizedIsInitialized;
         if (isInitialized != -1) return isInitialized == 1;
 
-        if (!hasValue()) {
-          memoizedIsInitialized = 0;
-          return false;
-        }
-        if (!getValue().isInitialized()) {
-          memoizedIsInitialized = 0;
-          return false;
+        if (hasValue()) {
+          if (!getValue().isInitialized()) {
+            memoizedIsInitialized = 0;
+            return false;
+          }
         }
         if (hasOtherKey()) {
           if (!getOtherKey().isInitialized()) {
@@ -10452,13 +10450,11 @@ public final class ReplicatedDataMessages {
         }
 
         public final boolean isInitialized() {
-          if (!hasValue()) {
-            
-            return false;
-          }
-          if (!getValue().isInitialized()) {
-            
-            return false;
+          if (hasValue()) {
+            if (!getValue().isInitialized()) {
+              
+              return false;
+            }
           }
           if (hasOtherKey()) {
             if (!getOtherKey().isInitialized()) {
@@ -10562,18 +10558,18 @@ public final class ReplicatedDataMessages {
           return this;
         }
 
-        // required .akka.cluster.ddata.OtherMessage value = 2;
+        // optional .akka.cluster.ddata.OtherMessage value = 2;
         private akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage value_ = akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage.getDefaultInstance();
         private akka.protobuf.SingleFieldBuilder<
             akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage, akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage.Builder, akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessageOrBuilder> valueBuilder_;
         /**
-         * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+         * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
          */
         public boolean hasValue() {
           return ((bitField0_ & 0x00000002) == 0x00000002);
         }
         /**
-         * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+         * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
          */
         public akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage getValue() {
           if (valueBuilder_ == null) {
@@ -10583,7 +10579,7 @@ public final class ReplicatedDataMessages {
           }
         }
         /**
-         * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+         * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
          */
         public Builder setValue(akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage value) {
           if (valueBuilder_ == null) {
@@ -10599,7 +10595,7 @@ public final class ReplicatedDataMessages {
           return this;
         }
         /**
-         * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+         * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
          */
         public Builder setValue(
             akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage.Builder builderForValue) {
@@ -10613,7 +10609,7 @@ public final class ReplicatedDataMessages {
           return this;
         }
         /**
-         * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+         * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
          */
         public Builder mergeValue(akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage value) {
           if (valueBuilder_ == null) {
@@ -10632,7 +10628,7 @@ public final class ReplicatedDataMessages {
           return this;
         }
         /**
-         * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+         * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
          */
         public Builder clearValue() {
           if (valueBuilder_ == null) {
@@ -10645,7 +10641,7 @@ public final class ReplicatedDataMessages {
           return this;
         }
         /**
-         * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+         * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
          */
         public akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage.Builder getValueBuilder() {
           bitField0_ |= 0x00000002;
@@ -10653,7 +10649,7 @@ public final class ReplicatedDataMessages {
           return getValueFieldBuilder().getBuilder();
         }
         /**
-         * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+         * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
          */
         public akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessageOrBuilder getValueOrBuilder() {
           if (valueBuilder_ != null) {
@@ -10663,7 +10659,7 @@ public final class ReplicatedDataMessages {
           }
         }
         /**
-         * <code>required .akka.cluster.ddata.OtherMessage value = 2;</code>
+         * <code>optional .akka.cluster.ddata.OtherMessage value = 2;</code>
          */
         private akka.protobuf.SingleFieldBuilder<
             akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage, akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessage.Builder, akka.cluster.ddata.protobuf.msg.ReplicatorMessages.OtherMessageOrBuilder> 
@@ -18396,7 +18392,7 @@ public final class ReplicatedDataMessages {
       "age\"\263\003\n\017ORMapDeltaGroup\022:\n\007entries\030\001 \003(\013" +
       "2).akka.cluster.ddata.ORMapDeltaGroup.En" +
       "try\032\243\001\n\010MapEntry\022\021\n\tstringKey\030\001 \001(\t\022/\n\005v" +
-      "alue\030\002 \002(\0132 .akka.cluster.ddata.OtherMes" +
+      "alue\030\002 \001(\0132 .akka.cluster.ddata.OtherMes" +
       "sage\022\016\n\006intKey\030\003 \001(\021\022\017\n\007longKey\030\004 \001(\022\0222\n" +
       "\010otherKey\030\005 \001(\0132 .akka.cluster.ddata.Oth" +
       "erMessage\032\275\001\n\005Entry\0223\n\toperation\030\001 \002(\0162 ",
diff --git a/akka-distributed-data/src/main/protobuf/ReplicatedDataMessages.proto b/akka-distributed-data/src/main/protobuf/ReplicatedDataMessages.proto
index 33efe55f5a..ca6b2fbdca 100644
--- a/akka-distributed-data/src/main/protobuf/ReplicatedDataMessages.proto
+++ b/akka-distributed-data/src/main/protobuf/ReplicatedDataMessages.proto
@@ -78,7 +78,7 @@ message ORMap {
 message ORMapDeltaGroup {
   message MapEntry {
     optional string stringKey = 1;
-    required OtherMessage value = 2;
+    optional OtherMessage value = 2;
     optional sint32 intKey = 3;
     optional sint64 longKey = 4;
     optional OtherMessage otherKey = 5;
diff --git a/akka-distributed-data/src/main/scala/akka/cluster/ddata/protobuf/ReplicatedDataSerializer.scala b/akka-distributed-data/src/main/scala/akka/cluster/ddata/protobuf/ReplicatedDataSerializer.scala
index 6138f73054..8d713e4633 100644
--- a/akka-distributed-data/src/main/scala/akka/cluster/ddata/protobuf/ReplicatedDataSerializer.scala
+++ b/akka-distributed-data/src/main/scala/akka/cluster/ddata/protobuf/ReplicatedDataSerializer.scala
@@ -585,6 +585,13 @@ class ReplicatedDataSerializer(val system: ExtendedActorSystem)
     }
   }
 
+  def singleKeyEntryFromProto[PEntry <: GeneratedMessage, A <: GeneratedMessage](entry: PEntry)(implicit eh: ProtoMapEntryReader[PEntry, A]): Any =
+    if (eh.hasStringKey(entry)) eh.getStringKey(entry)
+    else if (eh.hasIntKey(entry)) eh.getIntKey(entry)
+    else if (eh.hasLongKey(entry)) eh.getLongKey(entry)
+    else if (eh.hasOtherKey(entry)) otherMessageFromProto(eh.getOtherKey(entry))
+    else throw new IllegalArgumentException(s"Can't deserialize the key in the ORMap delta")
+
   // wire protocol is always DeltaGroup
   private def ormapPutFromBinary(bytes: Array[Byte]): ORMap.PutDeltaOp[Any, ReplicatedData] = {
     val group = ormapDeltaGroupFromBinary(bytes)
@@ -641,8 +648,8 @@ class ReplicatedDataSerializer(val system: ExtendedActorSystem)
         } else if (entry.getOperation == rd.ORMapDeltaOp.ORMapRemove) {
           ORMap.RemoveDeltaOp(ORSet.RemoveDeltaOp(orsetFromProto(entry.getUnderlying)), zeroTagFromCode(entry.getZeroTag))
         } else if (entry.getOperation == rd.ORMapDeltaOp.ORMapRemoveKey) {
-          val map = singleMapEntryFromProto(entry.getEntryData, (v: dm.OtherMessage) ⇒ otherMessageFromProto(v).asInstanceOf[ReplicatedData])
-          ORMap.RemoveKeyDeltaOp(ORSet.RemoveDeltaOp(orsetFromProto(entry.getUnderlying)), map.keySet.head, zeroTagFromCode(entry.getZeroTag))
+          val elem = singleKeyEntryFromProto(entry.getEntryData)
+          ORMap.RemoveKeyDeltaOp(ORSet.RemoveDeltaOp(orsetFromProto(entry.getUnderlying)), elem, zeroTagFromCode(entry.getZeroTag))
         } else if (entry.getOperation == rd.ORMapDeltaOp.ORMapUpdate) {
           val map = singleMapEntryFromProto(entry.getEntryData, (v: dm.OtherMessage) ⇒ otherMessageFromProto(v).asInstanceOf[ReplicatedDelta])
           ORMap.UpdateDeltaOp(ORSet.AddDeltaOp(orsetFromProto(entry.getUnderlying)), map, zeroTagFromCode(entry.getZeroTag))
@@ -690,6 +697,22 @@ class ReplicatedDataSerializer(val system: ExtendedActorSystem)
       }
     }
 
+    def createEntryWithKey(opType: rd.ORMapDeltaOp, u: ORSet[_], k: Any, zt: Int) = {
+      val entryDataBuilder = rd.ORMapDeltaGroup.MapEntry.newBuilder()
+      k match {
+        case key: String ⇒ entryDataBuilder.setStringKey(key)
+        case key: Int    ⇒ entryDataBuilder.setIntKey(key)
+        case key: Long   ⇒ entryDataBuilder.setLongKey(key)
+        case key         ⇒ entryDataBuilder.setOtherKey(otherMessageToProto(key))
+      }
+      val builder = rd.ORMapDeltaGroup.Entry.newBuilder()
+        .setOperation(opType)
+        .setUnderlying(orsetToProto(u))
+        .setZeroTag(zt)
+      builder.setEntryData(entryDataBuilder.build())
+      builder
+    }
+
     val b = rd.ORMapDeltaGroup.newBuilder()
     deltaGroup.ops.foreach {
       case ORMap.PutDeltaOp(op, pair, zt) ⇒
@@ -697,7 +720,7 @@ class ReplicatedDataSerializer(val system: ExtendedActorSystem)
       case ORMap.RemoveDeltaOp(op, zt) ⇒
         b.addEntries(createEntry(rd.ORMapDeltaOp.ORMapRemove, op.asInstanceOf[ORSet.RemoveDeltaOp[_]].underlying, Map.empty, zt.value))
       case ORMap.RemoveKeyDeltaOp(op, k, zt) ⇒
-        b.addEntries(createEntry(rd.ORMapDeltaOp.ORMapRemoveKey, op.asInstanceOf[ORSet.RemoveDeltaOp[_]].underlying, Map(k → k), zt.value))
+        b.addEntries(createEntryWithKey(rd.ORMapDeltaOp.ORMapRemoveKey, op.asInstanceOf[ORSet.RemoveDeltaOp[_]].underlying, k, zt.value))
       case ORMap.UpdateDeltaOp(op, m, zt) ⇒
         b.addEntries(createEntry(rd.ORMapDeltaOp.ORMapUpdate, op.asInstanceOf[ORSet.AddDeltaOp[_]].underlying, m, zt.value))
       case ORMap.DeltaGroup(u) ⇒
diff --git a/akka-distributed-data/src/test/scala/akka/cluster/ddata/protobuf/ReplicatedDataSerializerSpec.scala b/akka-distributed-data/src/test/scala/akka/cluster/ddata/protobuf/ReplicatedDataSerializerSpec.scala
index d5c97f4635..da86a68dc2 100644
--- a/akka-distributed-data/src/test/scala/akka/cluster/ddata/protobuf/ReplicatedDataSerializerSpec.scala
+++ b/akka-distributed-data/src/test/scala/akka/cluster/ddata/protobuf/ReplicatedDataSerializerSpec.scala
@@ -277,6 +277,7 @@ class ReplicatedDataSerializerSpec extends TestKit(ActorSystem(
       checkSerialization(ORMultiMap._emptyWithValueDeltas.addBinding(address1, 1, "A"))
       checkSerialization(ORMultiMap._emptyWithValueDeltas.addBinding(address1, 1L, "A"))
       checkSerialization(ORMultiMap._emptyWithValueDeltas.addBinding(address1, Flag(), "A"))
+      checkSerialization(ORMultiMap.emptyWithValueDeltas[String, String].addBinding(address1, "a", "A").remove(address1, "a").delta.get)
       checkSerialization(ORMultiMap.emptyWithValueDeltas[String, String]
         .addBinding(address1, "a", "A1")
         .put(address2, "b", Set("B1", "B2", "B3"))