diff --git a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcBoolean.java b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcBoolean.java
index 208e9239..40c36b39 100644
--- a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcBoolean.java
+++ b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcBoolean.java
@@ -3,7 +3,7 @@
 import lombok.RequiredArgsConstructor;
 
 @RequiredArgsConstructor
-public final class RpcBoolean extends RpcObject {
+public final class RpcBoolean implements RpcObject {
 
     private final boolean value;
 
diff --git a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcList.java b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcList.java
index c0b44db1..0743d45c 100644
--- a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcList.java
+++ b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcList.java
@@ -5,7 +5,7 @@
 import java.util.List;
 
 @RequiredArgsConstructor
-public final class RpcList extends RpcObject {
+public final class RpcList implements RpcObject {
 
     private final List<RpcObject> list;
 
diff --git a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcMap.java b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcMap.java
index 64f80daa..b517009f 100644
--- a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcMap.java
+++ b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcMap.java
@@ -5,7 +5,7 @@
 import java.util.Map;
 
 @RequiredArgsConstructor
-public final class RpcMap extends RpcObject {
+public final class RpcMap implements RpcObject {
 
     private final Map<String, RpcObject> map;
 
diff --git a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcNull.java b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcNull.java
index a1da460d..c272be03 100644
--- a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcNull.java
+++ b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcNull.java
@@ -3,7 +3,7 @@
 import java.util.List;
 import java.util.Map;
 
-public final class RpcNull extends RpcObject {
+public final class RpcNull implements RpcObject {
     @Override
     public boolean isNull() {
         return true;
diff --git a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcNumber.java b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcNumber.java
index 144054ea..b846c621 100644
--- a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcNumber.java
+++ b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcNumber.java
@@ -3,7 +3,7 @@
 import lombok.RequiredArgsConstructor;
 
 @RequiredArgsConstructor
-public final class RpcNumber extends RpcObject {
+public final class RpcNumber implements RpcObject {
 
     private final Number value;
 
diff --git a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcObject.java b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcObject.java
index 65e95e21..ab3c4139 100644
--- a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcObject.java
+++ b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcObject.java
@@ -3,76 +3,77 @@
 import java.util.List;
 import java.util.Map;
 
-public abstract class RpcObject {
+public interface RpcObject {
 
-    RpcObject() {
-    }
-
-    public boolean isNull() {
+    default boolean isNull() {
         return false;
     }
 
-    public boolean isBoolean() {
+    default boolean isBoolean() {
         return false;
     }
 
-    public boolean isList() {
+    default boolean isList() {
         return false;
     }
 
-    public boolean isMap() {
+    default boolean isMap() {
         return false;
     }
 
-    public boolean isNumber() {
+    default boolean isNumber() {
         return false;
     }
 
-    public boolean isString() {
+    default boolean isString() {
         return false;
     }
 
-    public Boolean asBoolean() {
+    default Boolean asBoolean() {
         throw new IllegalStateException();
     }
 
-    public List<RpcObject> asList() {
+    default List<RpcObject> asList() {
         throw new IllegalStateException();
     }
 
-    public Map<String, RpcObject> asMap() {
+    default Map<String, RpcObject> asMap() {
         throw new IllegalStateException();
     }
 
-    public Number asNumber() {
+    default Number asNumber() {
         throw new IllegalStateException();
     }
 
-    public String asString() {
+    default String asString() {
         throw new IllegalStateException();
     }
 
-    public static RpcObject ofNull() {
+    static RpcObject ofNull() {
         return new RpcNull();
     }
 
-    public static RpcObject of(boolean value) {
+    static RpcObject of(boolean value) {
         return new RpcBoolean(value);
     }
 
-    public static RpcObject of(List<RpcObject> list) {
+    static RpcObject of(List<RpcObject> list) {
         return list == null ? new RpcNull() : new RpcList(list);
     }
 
-    public static RpcObject of(Map<String, RpcObject> map) {
+    static RpcObject of(Map<String, RpcObject> map) {
         return map == null ? new RpcNull() : new RpcMap(map);
     }
 
-    public static RpcObject of(Number value) {
+    static RpcObject of(long value) {
+        return new RpcNumber(value);
+    }
+
+    static RpcObject of(Number value) {
         return value == null ? new RpcNull() : new RpcNumber(value);
     }
 
-    public static RpcObject of(String value) {
+    static RpcObject of(String value) {
         return value == null ? new RpcNull() : new RpcString(value);
     }
 
diff --git a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcString.java b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcString.java
index ffac54df..6e7b91e1 100644
--- a/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcString.java
+++ b/transport/src/main/java/com/strategyobject/substrateclient/transport/RpcString.java
@@ -3,7 +3,7 @@
 import lombok.RequiredArgsConstructor;
 
 @RequiredArgsConstructor
-public final class RpcString extends RpcObject {
+public final class RpcString implements RpcObject {
 
     private final String value;
 
diff --git a/transport/src/main/java/com/strategyobject/substrateclient/transport/coder/RpcObjectTypeAdapter.java b/transport/src/main/java/com/strategyobject/substrateclient/transport/coder/RpcObjectTypeAdapter.java
index eef97e8a..c6e13562 100644
--- a/transport/src/main/java/com/strategyobject/substrateclient/transport/coder/RpcObjectTypeAdapter.java
+++ b/transport/src/main/java/com/strategyobject/substrateclient/transport/coder/RpcObjectTypeAdapter.java
@@ -7,6 +7,8 @@
 import lombok.val;
 
 import java.io.IOException;
+import java.math.BigDecimal;
+import java.math.BigInteger;
 import java.util.ArrayList;
 import java.util.HashMap;
 
@@ -25,7 +27,7 @@ public RpcObject read(JsonReader in) throws IOException {
             case BOOLEAN:
                 return new RpcBoolean(in.nextBoolean());
             case NUMBER:
-                return new RpcNumber(in.nextDouble());
+                return new RpcNumber(parseNumber(in));
             case STRING:
                 return new RpcString(in.nextString());
             case BEGIN_ARRAY:
@@ -48,4 +50,21 @@ public RpcObject read(JsonReader in) throws IOException {
                 return new RpcMap(map);
         }
     }
+
+    private Number parseNumber(JsonReader in) throws IOException {
+        val value = in.nextString();
+        try {
+            return Long.parseLong(value);
+        } catch (NumberFormatException ignored) {
+            // Ignore
+        }
+
+        try {
+            return new BigInteger(value);
+        } catch (NumberFormatException ignored) {
+            // Ignore
+        }
+
+        return new BigDecimal(value);
+    }
 }
diff --git a/transport/src/test/java/com/strategyobject/substrateclient/transport/coder/RpcCoderTest.java b/transport/src/test/java/com/strategyobject/substrateclient/transport/coder/RpcCoderTest.java
index 38ef8171..206cb46c 100644
--- a/transport/src/test/java/com/strategyobject/substrateclient/transport/coder/RpcCoderTest.java
+++ b/transport/src/test/java/com/strategyobject/substrateclient/transport/coder/RpcCoderTest.java
@@ -30,6 +30,24 @@ void decodeNullResult() {
                 .isEqualTo(expected);
     }
 
+    @Test
+    void DecodeLongNumber() {
+        val json = "{\n" +
+                "    \"result\": 506884800,\n" +
+                "    \"id\": 0,\n" +
+                "    \"jsonrpc\": \"3.0\"\n" +
+                "}";
+        val actual = RpcCoder.decodeJson(json);
+
+        val expected = new JsonRpcResponse();
+        expected.jsonrpc = "3.0";
+        expected.id = 0;
+        expected.result = RpcObject.of(506884800);
+        assertThat(actual)
+                .usingRecursiveComparison()
+                .isEqualTo(expected);
+    }
+
     @Test
     void decodeJson() {
         val json = "{\n" +