diff --git a/src/main/kotlin/io/emeraldpay/dshackle/upstream/calls/DefaultEthereumMethods.kt b/src/main/kotlin/io/emeraldpay/dshackle/upstream/calls/DefaultEthereumMethods.kt
index 59b13f72..ca75c7a8 100644
--- a/src/main/kotlin/io/emeraldpay/dshackle/upstream/calls/DefaultEthereumMethods.kt
+++ b/src/main/kotlin/io/emeraldpay/dshackle/upstream/calls/DefaultEthereumMethods.kt
@@ -129,16 +129,16 @@ class DefaultEthereumMethods(
             "eth_chainId" -> {
                 when {
                     Chain.ETHEREUM == chain -> {
-                        "0x0"
+                        "\"0x0\""
                     }
                     Chain.ETHEREUM_CLASSIC == chain -> {
-                        "0x3d"
+                        "\"0x3d\""
                     }
                     Chain.TESTNET_MORDEN == chain -> {
-                        "0x3c"
+                        "\"0x3c\""
                     }
                     Chain.TESTNET_KOVAN == chain -> {
-                        "0x2a"
+                        "\"0x2a\""
                     }
                     else -> throw RpcException(-32602, "Invalid chain")
                 }
diff --git a/src/test/groovy/io/emeraldpay/dshackle/upstream/calls/DefaultEthereumMethodsSpec.groovy b/src/test/groovy/io/emeraldpay/dshackle/upstream/calls/DefaultEthereumMethodsSpec.groovy
index aa6240f3..8779d3d9 100644
--- a/src/test/groovy/io/emeraldpay/dshackle/upstream/calls/DefaultEthereumMethodsSpec.groovy
+++ b/src/test/groovy/io/emeraldpay/dshackle/upstream/calls/DefaultEthereumMethodsSpec.groovy
@@ -19,8 +19,8 @@ class DefaultEthereumMethodsSpec extends Specification {
         new String(new DefaultEthereumMethods(chain).executeHardcoded("eth_chainId")) == id
         where:
         chain                  | id
-        Chain.ETHEREUM         | "0x0"
-        Chain.ETHEREUM_CLASSIC | "0x3d"
-        Chain.TESTNET_KOVAN    | "0x2a"
+        Chain.ETHEREUM         | '"0x0"'
+        Chain.ETHEREUM_CLASSIC | '"0x3d"'
+        Chain.TESTNET_KOVAN    | '"0x2a"'
     }
 }