diff --git a/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/methods/AdminAddPeer.java b/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/methods/AdminAddPeer.java
index 8f626ee154..28e6d71358 100644
--- a/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/methods/AdminAddPeer.java
+++ b/ethereum/jsonrpc/src/main/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/methods/AdminAddPeer.java
@@ -44,6 +44,9 @@ public class AdminAddPeer implements JsonRpcMethod {
 
   @Override
   public JsonRpcResponse response(final JsonRpcRequest req) {
+    if (req.getParamLength() != 1) {
+      return new JsonRpcErrorResponse(req.getId(), JsonRpcError.INVALID_PARAMS);
+    }
     try {
       final String enodeString = parameters.required(req.getParams(), 0, String.class);
       final Peer peer = DefaultPeer.fromURI(enodeString);
diff --git a/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/methods/AdminAddPeerTest.java b/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/methods/AdminAddPeerTest.java
index cb471f1adc..6082965a2c 100644
--- a/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/methods/AdminAddPeerTest.java
+++ b/ethereum/jsonrpc/src/test/java/tech/pegasys/pantheon/ethereum/jsonrpc/internal/methods/AdminAddPeerTest.java
@@ -91,6 +91,35 @@ public class AdminAddPeerTest {
     assertThat(actualResponse).isEqualToComparingFieldByField(expectedResponse);
   }
 
+  @Test
+  public void requestRefusesListOfNodes() {
+    final JsonRpcRequest request =
+        new JsonRpcRequest(
+            "2.0",
+            "admin_addPeer",
+            new String[] {
+              "enode://"
+                  + "00000000000000000000000000000000"
+                  + "00000000000000000000000000000000"
+                  + "00000000000000000000000000000000"
+                  + "00000000000000000000000000000000"
+                  + "@127.0.0.1:30303",
+              "enode://"
+                  + "00000000000000000000000000000000"
+                  + "00000000000000000000000000000000"
+                  + "00000000000000000000000000000000"
+                  + "00000000000000000000000000000001"
+                  + "@127.0.0.2:30303"
+            });
+
+    final JsonRpcResponse expectedResponse =
+        new JsonRpcErrorResponse(request.getId(), JsonRpcError.INVALID_PARAMS);
+
+    final JsonRpcResponse actualResponse = method.response(request);
+
+    assertThat(actualResponse).isEqualToComparingFieldByField(expectedResponse);
+  }
+
   @Test
   public void requestReturnsFalseIfAddFails() {
     when(p2pNetwork.addMaintainConnectionPeer(any())).thenReturn(false);