diff --git a/packages/grpc-native-core/index.d.ts b/packages/grpc-native-core/index.d.ts
index 69c423d8..73a685cd 100644
--- a/packages/grpc-native-core/index.d.ts
+++ b/packages/grpc-native-core/index.d.ts
@@ -66,7 +66,7 @@ declare module "grpc" {
    * - Anything else becomes the relevant reflection object that ProtoBuf.js would create
    */
   export interface GrpcObject {
-    [name: string]: GrpcObject | typeof Client | Message;
+    [name: string]: GrpcObject | typeof Client | Message<any>;
   }
 
   /**
@@ -573,12 +573,12 @@ declare module "grpc" {
     /**
      * The server's private key
      */
-    privateKey: Buffer;
+    private_key: Buffer;
 
     /**
      * The server's certificate chain
      */
-    certChain: Buffer;
+    cert_chain: Buffer;
   }
 
   /**
diff --git a/packages/grpc-native-core/index.js b/packages/grpc-native-core/index.js
index 7810b7bf..fa07baeb 100644
--- a/packages/grpc-native-core/index.js
+++ b/packages/grpc-native-core/index.js
@@ -219,8 +219,8 @@ exports.ServerCredentials = grpc.ServerCredentials;
 /**
  * A private key and certificate pair
  * @typedef {Object} grpc.ServerCredentials~keyCertPair
- * @property {Buffer} privateKey The server's private key
- * @property {Buffer} certChain The server's certificate chain
+ * @property {Buffer} private_key The server's private key
+ * @property {Buffer} cert_chain The server's certificate chain
  */
 
 /**
diff --git a/packages/grpc-native-core/src/client.js b/packages/grpc-native-core/src/client.js
index b9de0ab5..a917cbc9 100644
--- a/packages/grpc-native-core/src/client.js
+++ b/packages/grpc-native-core/src/client.js
@@ -513,13 +513,23 @@ exports.Client = Client;
 Client.prototype.makeUnaryRequest = function(method, serialize, deserialize,
                                              argument, metadata, options,
                                              callback) {
-  if (!(metadata instanceof Metadata)) {
-    callback = options;
-    options = metadata;
-    metadata = new Metadata();
-  }
   if (options instanceof Function) {
     callback = options;
+    if (metadata instanceof Metadata) {
+      options = {};
+    } else {
+      options = metadata;
+      metadata = new Metadata();
+    }
+  } else if (metadata instanceof Function) {
+    callback = metadata;
+    metadata = new Metadata();
+    options = {};
+  }
+  if (!metadata) {
+    metadata = new Metadata();
+  }
+  if (!options) {
     options = {};
   }
   if (!((metadata instanceof Metadata) &&
@@ -599,13 +609,23 @@ Client.prototype.makeUnaryRequest = function(method, serialize, deserialize,
 Client.prototype.makeClientStreamRequest = function(method, serialize,
                                                       deserialize, metadata,
                                                       options, callback) {
-  if (!(metadata instanceof Metadata)) {
-    callback = options;
-    options = metadata;
-    metadata = new Metadata();
-  }
   if (options instanceof Function) {
     callback = options;
+    if (metadata instanceof Metadata) {
+      options = {};
+    } else {
+      options = metadata;
+      metadata = new Metadata();
+    }
+  } else if (metadata instanceof Function) {
+    callback = metadata;
+    metadata = new Metadata();
+    options = {};
+  }
+  if (!metadata) {
+    metadata = new Metadata();
+  }
+  if (!options) {
     options = {};
   }
   if (!((metadata instanceof Metadata) &&
diff --git a/packages/grpc-native-core/src/grpc_extension.js b/packages/grpc-native-core/src/grpc_extension.js
index 46e2721d..9a023b7c 100644
--- a/packages/grpc-native-core/src/grpc_extension.js
+++ b/packages/grpc-native-core/src/grpc_extension.js
@@ -31,17 +31,26 @@ var binding;
 try {
   binding = require(binding_path);
 } catch (e) {
-  var fs = require('fs');
-  var searchPath = path.dirname(path.dirname(binding_path));
-  var searchName = path.basename(path.dirname(binding_path));
-  var foundNames = fs.readdirSync(searchPath);
+  let fs = require('fs');
+  let searchPath = path.dirname(path.dirname(binding_path));
+  let searchName = path.basename(path.dirname(binding_path));
+  let foundNames;
+  try {
+    foundNames = fs.readdirSync(searchPath);
+  } catch (readDirError) {
+    let message = `The gRPC binary module was not installed. This may be fixed by running "npm rebuild"
+Original error: ${e.message}`;
+    let error = new Error(message);
+    error.code = e.code;
+    throw error;
+  }
   if (foundNames.indexOf(searchName) === -1) {
-    var message = `Failed to load gRPC binary module because it was not installed for the current system
+    let message = `Failed to load gRPC binary module because it was not installed for the current system
 Expected directory: ${searchName}
 Found: [${foundNames.join(', ')}]
 This problem can often be fixed by running "npm rebuild" on the current system
 Original error: ${e.message}`;
-    var error = new Error(message);
+    let error = new Error(message);
     error.code = e.code;
     throw error;
   } else {
diff --git a/test/api/surface_test.js b/test/api/surface_test.js
index 3bffaf8e..92802435 100644
--- a/test/api/surface_test.js
+++ b/test/api/surface_test.js
@@ -506,6 +506,116 @@ describe('Echo metadata', function() {
       done();
     });
   });
+  describe('Call argument handling', function() {
+    describe('Unary call', function() {
+      it('Should handle undefined options', function(done) {
+        var call = client.unary({}, metadata, undefined, function(err, data) {
+          assert.ifError(err);
+        });
+        call.on('metadata', function(metadata) {
+          assert.deepEqual(metadata.get('key'), ['value']);
+          done();
+        });
+      });
+      it('Should handle two undefined arguments', function(done) {
+        var call = client.unary({}, undefined, undefined, function(err, data) {
+          assert.ifError(err);
+        });
+        call.on('metadata', function(metadata) {
+          done();
+        });
+      });
+      it('Should handle one undefined argument', function(done) {
+        var call = client.unary({}, undefined, function(err, data) {
+          assert.ifError(err);
+        });
+        call.on('metadata', function(metadata) {
+          done();
+        });
+      });
+    });
+    describe('Client stream call', function() {
+      it('Should handle undefined options', function(done) {
+        var call = client.clientStream(metadata, undefined, function(err, data) {
+          assert.ifError(err);
+        });
+        call.on('metadata', function(metadata) {
+          assert.deepEqual(metadata.get('key'), ['value']);
+          done();
+        });
+        call.end();
+      });
+      it('Should handle two undefined arguments', function(done) {
+        var call = client.clientStream(undefined, undefined, function(err, data) {
+          assert.ifError(err);
+        });
+        call.on('metadata', function(metadata) {
+          done();
+        });
+        call.end();
+      });
+      it('Should handle one undefined argument', function(done) {
+        var call = client.clientStream(undefined, function(err, data) {
+          assert.ifError(err);
+        });
+        call.on('metadata', function(metadata) {
+          done();
+        });
+        call.end();
+      });
+    });
+    describe('Server stream call', function() {
+      it('Should handle undefined options', function(done) {
+        var call = client.serverStream({}, metadata, undefined);
+        call.on('data', function() {});
+        call.on('metadata', function(metadata) {
+          assert.deepEqual(metadata.get('key'), ['value']);
+          done();
+        });
+      });
+      it('Should handle two undefined arguments', function(done) {
+        var call = client.serverStream({}, undefined, undefined);
+        call.on('data', function() {});
+        call.on('metadata', function(metadata) {
+          done();
+        });
+      });
+      it('Should handle one undefined argument', function(done) {
+        var call = client.serverStream({}, undefined);
+        call.on('data', function() {});
+        call.on('metadata', function(metadata) {
+          done();
+        });
+      });
+    });
+    describe('Bidi stream call', function() {
+      it('Should handle undefined options', function(done) {
+        var call = client.bidiStream(metadata, undefined);
+        call.on('data', function() {});
+        call.on('metadata', function(metadata) {
+          assert.deepEqual(metadata.get('key'), ['value']);
+          done();
+        });
+        call.end();
+      });
+      it('Should handle two undefined arguments', function(done) {
+        var call = client.bidiStream(undefined, undefined);
+        call.on('data', function() {});
+        call.on('metadata', function(metadata) {
+          done();
+        });
+        call.end();
+      });
+      it('Should handle one undefined argument', function(done) {
+        var call = client.bidiStream(undefined);
+        call.on('data', function() {});
+        call.on('metadata', function(metadata) {
+          done();
+        });
+        call.end();
+      });
+    });
+  });
 });
 describe('Client malformed response handling', function() {
   var server;