diff --git a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MetaBuilder.kt b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MetaBuilder.kt
index 671d1f13..c5ad3831 100644
--- a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MetaBuilder.kt
+++ b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MetaBuilder.kt
@@ -15,55 +15,55 @@ class MetaBuilder : AbstractMutableMeta<MetaBuilder>() {
     override fun wrapNode(meta: Meta): MetaBuilder = if (meta is MetaBuilder) meta else meta.builder()
     override fun empty(): MetaBuilder = MetaBuilder()
 
-    infix fun String.put(value: Value){
-        set(this,value)
+    infix fun String.put(value: Value?) {
+        set(this, value)
     }
 
-    infix fun String.put(string: String){
-        set(this,string.asValue())
+    infix fun String.put(string: String?) {
+        set(this, string?.asValue())
     }
 
-    infix fun String.put(number: Number){
-        set(this,number.asValue())
+    infix fun String.put(number: Number?) {
+        set(this, number?.asValue())
     }
 
-    infix fun String.put(boolean: Boolean){
-        set(this, boolean.asValue())
+    infix fun String.put(boolean: Boolean?) {
+        set(this, boolean?.asValue())
     }
 
-    infix fun String.put(enum: Enum<*>){
+    infix fun String.put(enum: Enum<*>) {
         set(this, EnumValue(enum))
     }
 
     @JvmName("putValues")
-    infix fun String.put(iterable: Iterable<Value>){
+    infix fun String.put(iterable: Iterable<Value>) {
         set(this, iterable.asValue())
     }
 
     @JvmName("putNumbers")
-    infix fun String.put(iterable: Iterable<Number>){
+    infix fun String.put(iterable: Iterable<Number>) {
         set(this, iterable.map { it.asValue() }.asValue())
     }
 
     @JvmName("putStrings")
-    infix fun String.put(iterable: Iterable<String>){
+    infix fun String.put(iterable: Iterable<String>) {
         set(this, iterable.map { it.asValue() }.asValue())
     }
 
-    infix fun String.put(array: DoubleArray){
+    infix fun String.put(array: DoubleArray) {
         set(this, array.asValue())
     }
 
-    infix fun String.putValue(any: Any?){
+    infix fun String.putValue(any: Any?) {
         set(this, Value.of(any))
     }
 
-    infix fun String.put(meta: Meta) {
+    infix fun String.put(meta: Meta?) {
         this@MetaBuilder[this] = meta
     }
 
-    infix fun String.put(repr: MetaRepr){
-        set(this,repr.toMeta())
+    infix fun String.put(repr: MetaRepr?) {
+        set(this, repr?.toMeta())
     }
 
     @JvmName("putMetas")
@@ -75,37 +75,37 @@ class MetaBuilder : AbstractMutableMeta<MetaBuilder>() {
         this@MetaBuilder[this] = MetaBuilder().apply(metaBuilder)
     }
 
-    infix fun Name.put(value: Value){
-        set(this,value)
+    infix fun Name.put(value: Value?) {
+        set(this, value)
     }
 
-    infix fun Name.put(string: String){
-        set(this,string.asValue())
+    infix fun Name.put(string: String?) {
+        set(this, string?.asValue())
     }
 
-    infix fun Name.put(number: Number){
-        set(this,number.asValue())
+    infix fun Name.put(number: Number?) {
+        set(this, number?.asValue())
     }
 
-    infix fun Name.put(boolean: Boolean){
-        set(this, boolean.asValue())
+    infix fun Name.put(boolean: Boolean?) {
+        set(this, boolean?.asValue())
     }
 
-    infix fun Name.put(enum: Enum<*>){
+    infix fun Name.put(enum: Enum<*>) {
         set(this, EnumValue(enum))
     }
 
     @JvmName("putValues")
-    infix fun Name.put(iterable: Iterable<Value>){
+    infix fun Name.put(iterable: Iterable<Value>) {
         set(this, iterable.asValue())
     }
 
-    infix fun Name.put(meta: Meta) {
+    infix fun Name.put(meta: Meta?) {
         this@MetaBuilder[this] = meta
     }
 
-    infix fun Name.put(repr: MetaRepr){
-        set(this,repr.toMeta())
+    infix fun Name.put(repr: MetaRepr?) {
+        set(this, repr?.toMeta())
     }
 
     @JvmName("putMetas")