diff --git a/packages/google-cloud-monitoring/protos/protos.d.ts b/packages/google-cloud-monitoring/protos/protos.d.ts
index 37434fe1367..8f11bab8f48 100644
--- a/packages/google-cloud-monitoring/protos/protos.d.ts
+++ b/packages/google-cloud-monitoring/protos/protos.d.ts
@@ -15945,6 +15945,9 @@ export namespace google {
 
             /** FieldDescriptorProto options */
             options?: (google.protobuf.IFieldOptions|null);
+
+            /** FieldDescriptorProto proto3Optional */
+            proto3Optional?: (boolean|null);
         }
 
         /** Represents a FieldDescriptorProto. */
@@ -15986,6 +15989,9 @@ export namespace google {
             /** FieldDescriptorProto options. */
             public options?: (google.protobuf.IFieldOptions|null);
 
+            /** FieldDescriptorProto proto3Optional. */
+            public proto3Optional: boolean;
+
             /**
              * Creates a new FieldDescriptorProto instance using the specified properties.
              * @param [properties] Properties to set
diff --git a/packages/google-cloud-monitoring/protos/protos.js b/packages/google-cloud-monitoring/protos/protos.js
index 802170e9dfd..66bf33fddb5 100644
--- a/packages/google-cloud-monitoring/protos/protos.js
+++ b/packages/google-cloud-monitoring/protos/protos.js
@@ -38718,6 +38718,7 @@
                  * @property {number|null} [oneofIndex] FieldDescriptorProto oneofIndex
                  * @property {string|null} [jsonName] FieldDescriptorProto jsonName
                  * @property {google.protobuf.IFieldOptions|null} [options] FieldDescriptorProto options
+                 * @property {boolean|null} [proto3Optional] FieldDescriptorProto proto3Optional
                  */
     
                 /**
@@ -38815,6 +38816,14 @@
                  */
                 FieldDescriptorProto.prototype.options = null;
     
+                /**
+                 * FieldDescriptorProto proto3Optional.
+                 * @member {boolean} proto3Optional
+                 * @memberof google.protobuf.FieldDescriptorProto
+                 * @instance
+                 */
+                FieldDescriptorProto.prototype.proto3Optional = false;
+    
                 /**
                  * Creates a new FieldDescriptorProto instance using the specified properties.
                  * @function create
@@ -38859,6 +38868,8 @@
                         writer.uint32(/* id 9, wireType 0 =*/72).int32(message.oneofIndex);
                     if (message.jsonName != null && Object.hasOwnProperty.call(message, "jsonName"))
                         writer.uint32(/* id 10, wireType 2 =*/82).string(message.jsonName);
+                    if (message.proto3Optional != null && Object.hasOwnProperty.call(message, "proto3Optional"))
+                        writer.uint32(/* id 17, wireType 0 =*/136).bool(message.proto3Optional);
                     return writer;
                 };
     
@@ -38923,6 +38934,9 @@
                         case 8:
                             message.options = $root.google.protobuf.FieldOptions.decode(reader, reader.uint32());
                             break;
+                        case 17:
+                            message.proto3Optional = reader.bool();
+                            break;
                         default:
                             reader.skipType(tag & 7);
                             break;
@@ -39017,6 +39031,9 @@
                         if (error)
                             return "options." + error;
                     }
+                    if (message.proto3Optional != null && message.hasOwnProperty("proto3Optional"))
+                        if (typeof message.proto3Optional !== "boolean")
+                            return "proto3Optional: boolean expected";
                     return null;
                 };
     
@@ -39139,6 +39156,8 @@
                             throw TypeError(".google.protobuf.FieldDescriptorProto.options: object expected");
                         message.options = $root.google.protobuf.FieldOptions.fromObject(object.options);
                     }
+                    if (object.proto3Optional != null)
+                        message.proto3Optional = Boolean(object.proto3Optional);
                     return message;
                 };
     
@@ -39166,6 +39185,7 @@
                         object.options = null;
                         object.oneofIndex = 0;
                         object.jsonName = "";
+                        object.proto3Optional = false;
                     }
                     if (message.name != null && message.hasOwnProperty("name"))
                         object.name = message.name;
@@ -39187,6 +39207,8 @@
                         object.oneofIndex = message.oneofIndex;
                     if (message.jsonName != null && message.hasOwnProperty("jsonName"))
                         object.jsonName = message.jsonName;
+                    if (message.proto3Optional != null && message.hasOwnProperty("proto3Optional"))
+                        object.proto3Optional = message.proto3Optional;
                     return object;
                 };
     
@@ -40980,7 +41002,7 @@
                  * @memberof google.protobuf.FileOptions
                  * @instance
                  */
-                FileOptions.prototype.ccEnableArenas = false;
+                FileOptions.prototype.ccEnableArenas = true;
     
                 /**
                  * FileOptions objcClassPrefix.
@@ -41466,7 +41488,7 @@
                         object.javaGenerateEqualsAndHash = false;
                         object.deprecated = false;
                         object.javaStringCheckUtf8 = false;
-                        object.ccEnableArenas = false;
+                        object.ccEnableArenas = true;
                         object.objcClassPrefix = "";
                         object.csharpNamespace = "";
                         object.swiftPrefix = "";
diff --git a/packages/google-cloud-monitoring/protos/protos.json b/packages/google-cloud-monitoring/protos/protos.json
index fcccb5c697b..9c508bf23e7 100644
--- a/packages/google-cloud-monitoring/protos/protos.json
+++ b/packages/google-cloud-monitoring/protos/protos.json
@@ -3614,6 +3614,10 @@
                 "options": {
                   "type": "FieldOptions",
                   "id": 8
+                },
+                "proto3Optional": {
+                  "type": "bool",
+                  "id": 17
                 }
               },
               "nested": {
@@ -3849,7 +3853,7 @@
                   "type": "bool",
                   "id": 31,
                   "options": {
-                    "default": false
+                    "default": true
                   }
                 },
                 "objcClassPrefix": {
diff --git a/packages/google-cloud-monitoring/synth.metadata b/packages/google-cloud-monitoring/synth.metadata
index 1374e530cad..cab232128e6 100644
--- a/packages/google-cloud-monitoring/synth.metadata
+++ b/packages/google-cloud-monitoring/synth.metadata
@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/nodejs-monitoring.git",
-        "sha": "4945b6c0bac9783e3432ee395b7dee70693fa591"
+        "sha": "dc4ca8ae954b1600e4c1987f96c27ef965383467"
       }
     },
     {