diff --git a/README.md b/README.md
index e7d20461..8102eb85 100644
--- a/README.md
+++ b/README.md
@@ -346,6 +346,7 @@ A brief summary of the available options follows.
 | OP_VERBOSITY                | A bitmask of client constants controlling raw message output to the console. |
 | OP_COMBINE_COOKIES          | A boolean (default: `true`) controlling whether or not cookie headers are combined into a single header when sending requests. |
 | OP_CRYPTO                   | An array controlling TLS encryption options. |
+| OP_DEFAULT_USER_AGENT       | A string set for each request's User-Agent if a UA has not already been provided. |
 
 
 ### Miscellaneous
diff --git a/lib/Client.php b/lib/Client.php
index 098f3f54..50e39c0f 100644
--- a/lib/Client.php
+++ b/lib/Client.php
@@ -487,7 +487,7 @@ private function parseSocketData(RequestCycle $cycle) {
                 } else {
                     $this->assignParsedResponse($cycle, $parsedResponseArr);
                 }
-                
+
                 if ($cycle->parser->getBuffer()) {
                     $this->reactor->immediately(function() use ($cycle) {
                         $this->parseSocketData($cycle);
@@ -992,6 +992,9 @@ public function setOption($option, $value) {
             case self::OP_CRYPTO:
                 $this->options[self::OP_CRYPTO] = (array) $value;
                 break;
+            case self::OP_DEFAULT_USER_AGENT:
+                $this->options[self::OP_DEFAULT_USER_AGENT] = (string) $value;
+                break;
             default:
                 throw new \DomainException(
                     sprintf("Unknown option: %s", $option)