diff --git a/jstests/sharding/addshard2.js b/jstests/sharding/addshard2.js
index d6487c6d366a3..dab39ec42400a 100644
--- a/jstests/sharding/addshard2.js
+++ b/jstests/sharding/addshard2.js
@@ -25,6 +25,15 @@ var rs4 = new ReplSetTest({ 'name': 'admin', nodes: 3, startPort: 31209 });
 rs4.startSet();
 rs4.initiate();
 
+// replica set with configServer: true should *not* be allowed to be added as a shard
+var rs5 = new ReplSetTest({ 'name': 'csrs', nodes: 3, startPort: 31212 });
+rs5.startSet();
+var conf = rs5.getReplSetConfig();
+conf.configServer = true;
+conf.settings = {protocolVersion: 1};
+rs5.initiate(conf);
+
+
 // step 1. name given
 assert(s.admin.runCommand({"addshard" : getHostName()+":" + conn1.port, "name" : "bar"}).ok,
        "failed to add shard in step 1");
@@ -82,8 +91,12 @@ var wRes = s.getDB('test').foo.insert({ x: 1 });
 assert(!wRes.hasWriteError() && wRes.nInserted === 1,
        'failed to insert document into "test.foo" unsharded collection');
 
+// SERVER-19545 Should not be able to add config server replsets as shards.
+assert.commandFailed(s.admin.runCommand({addshard: rs5.getURL()}));
+
 s.stop();
 rs1.stopSet();
 rs2.stopSet();
 rs3.stopSet();
 rs4.stopSet();
+rs5.stopSet();
\ No newline at end of file
diff --git a/src/mongo/db/repl/topology_coordinator_impl.cpp b/src/mongo/db/repl/topology_coordinator_impl.cpp
index 26433cc4f16c3..dec1362d2d04d 100644
--- a/src/mongo/db/repl/topology_coordinator_impl.cpp
+++ b/src/mongo/db/repl/topology_coordinator_impl.cpp
@@ -1503,6 +1503,10 @@ void TopologyCoordinatorImpl::prepareStatusResponse(const ReplicationExecutor::C
         response->append("syncingTo", _syncSource.toString());
     }
 
+    if (_rsConfig.isConfigServer()) {
+        response->append("configServer", true);
+    }
+
     response->append("members", membersOut);
     *result = Status::OK();
 }
diff --git a/src/mongo/s/catalog/catalog_manager.cpp b/src/mongo/s/catalog/catalog_manager.cpp
index 2eb60e4551919..8b17a81149646 100644
--- a/src/mongo/s/catalog/catalog_manager.cpp
+++ b/src/mongo/s/catalog/catalog_manager.cpp
@@ -36,6 +36,7 @@
 
 #include "mongo/base/status.h"
 #include "mongo/base/status_with.h"
+#include "mongo/bson/util/bson_extract.h"
 #include "mongo/client/read_preference.h"
 #include "mongo/client/remote_command_targeter.h"
 #include "mongo/client/replica_set_monitor.h"
@@ -182,20 +183,34 @@ StatusWith<ShardType> validateHostAsShard(ShardRegistry* shardRegistry,
     }
 
     // Is it a mongos config server?
-    if (foundSetName.empty()) {
-        cmdStatus = shardRegistry->runCommand(shardHost, "admin", BSON("replSetGetStatus" << 1));
-        if (!cmdStatus.isOK()) {
-            return cmdStatus.getStatus();
-        }
+    cmdStatus = shardRegistry->runCommand(shardHost, "admin", BSON("replSetGetStatus" << 1));
+    if (!cmdStatus.isOK()) {
+        return cmdStatus.getStatus();
+    }
 
-        BSONObj res = cmdStatus.getValue();
+    BSONObj res = cmdStatus.getValue();
 
-        if (!getStatusFromCommandResult(res).isOK() && (res["info"].type() == String) &&
-            (res["info"].String() == "configsvr")) {
+    if (getStatusFromCommandResult(res).isOK()) {
+        bool isConfigServer;
+        Status status =
+            bsonExtractBooleanFieldWithDefault(res, "configServer", false, &isConfigServer);
+        if (!status.isOK()) {
+            return Status(status.code(),
+                          str::stream() << "replSetGetStatus returned invalid \"configServer\" "
+                                        << "field when attempting to add "
+                                        << connectionString.toString()
+                                        << " as a shard: " << status.reason());
+        }
+
+        if (isConfigServer) {
             return {ErrorCodes::BadValue,
-                    "the specified mongod is a legacy-style config "
-                    "server and cannot be used as a shard server"};
+                    str::stream() << "Cannot add " << connectionString.toString()
+                                  << " as a shard since it is part of a config server replica set"};
         }
+    } else if ((res["info"].type() == String) && (res["info"].String() == "configsvr")) {
+        return {ErrorCodes::BadValue,
+                "the specified mongod is a legacy-style config "
+                "server and cannot be used as a shard server"};
     }
 
     // If the shard is part of a replica set, make sure all the hosts mentioned in the connection