diff --git a/messages/csharp/src/Deltix.Timebase.Messages/EPAM.Deltix.Timebase.Messages.Schema/RecordClassDescriptor.cs b/messages/csharp/src/Deltix.Timebase.Messages/EPAM.Deltix.Timebase.Messages.Schema/RecordClassDescriptor.cs
index 7f6e80c6b..acf4585e2 100644
--- a/messages/csharp/src/Deltix.Timebase.Messages/EPAM.Deltix.Timebase.Messages.Schema/RecordClassDescriptor.cs
+++ b/messages/csharp/src/Deltix.Timebase.Messages/EPAM.Deltix.Timebase.Messages.Schema/RecordClassDescriptor.cs
@@ -107,7 +107,7 @@ public virtual Boolean IsAbstract
         /// Defines if current RecordClassDescriptor is content class.
         /// </summary>
         [SchemaElement(Name=null, Title=null, Description=null)]
-        [SchemaType(Encoding=null, IsNullable=false, DataType=SchemaDataType.Default, Minimum=null, Maximum=null, NestedTypes=new Type[0])]
+        [SchemaType(Encoding=null, IsNullable=true, DataType=SchemaDataType.Default, Minimum=null, Maximum=null, NestedTypes=new Type[0])]
         public virtual Boolean IsContentClass
         {
             get
diff --git a/messages/schema/EPAM/Deltix/Timebase/Messages/Schema/RecordClassDescriptor.lux b/messages/schema/EPAM/Deltix/Timebase/Messages/Schema/RecordClassDescriptor.lux
index f77f1daef..c31917a90 100644
--- a/messages/schema/EPAM/Deltix/Timebase/Messages/Schema/RecordClassDescriptor.lux
+++ b/messages/schema/EPAM/Deltix/Timebase/Messages/Schema/RecordClassDescriptor.lux
@@ -22,7 +22,7 @@ class RecordClassDescriptor : ClassDescriptor {
 
     /// Defines if current RecordClassDescriptor is content class.
     [SchemaElement]
-    [SchemaType(IsNullable=false)]
+    [SchemaType(IsNullable=true)]
     Boolean IsContentClass;
 
     /// List of fields of a class.
diff --git a/messages/src/main/java/com/epam/deltix/timebase/messages/InstrumentMessage.java b/messages/src/main/java/com/epam/deltix/timebase/messages/InstrumentMessage.java
index cbe7a2c3d..432ff3bf0 100644
--- a/messages/src/main/java/com/epam/deltix/timebase/messages/InstrumentMessage.java
+++ b/messages/src/main/java/com/epam/deltix/timebase/messages/InstrumentMessage.java
@@ -72,10 +72,10 @@ public long                 getNanoTime() {
     }
 
     /**
-     * Indicated that this message has defined point in time.
+     * Indicated that this message has defined nanoseconds component of the time.
      */
     public boolean hasNanoTime() {
-        return timestamp != TIMESTAMP_UNKNOWN;
+        return nanoTime != 0;
     }
 
     /**
diff --git a/messages/src/main/java/com/epam/deltix/timebase/messages/schema/RecordClassDescriptor.java b/messages/src/main/java/com/epam/deltix/timebase/messages/schema/RecordClassDescriptor.java
index e7ea6955e..e38ee0c9c 100644
--- a/messages/src/main/java/com/epam/deltix/timebase/messages/schema/RecordClassDescriptor.java
+++ b/messages/src/main/java/com/epam/deltix/timebase/messages/schema/RecordClassDescriptor.java
@@ -123,7 +123,7 @@ public void nullifyIsAbstract() {
    */
   @SchemaElement
   @SchemaType(
-      isNullable = false
+      isNullable = true
   )
   public boolean isContentClass() {
     return isContentClass == 1;