diff --git a/src/FlexibleHttpClient.php b/src/FlexibleHttpClient.php
index 3979868..d6f1862 100644
--- a/src/FlexibleHttpClient.php
+++ b/src/FlexibleHttpClient.php
@@ -25,7 +25,7 @@ final class FlexibleHttpClient implements HttpClient, HttpAsyncClient
     public function __construct($client)
     {
         if (!($client instanceof ClientInterface) && !($client instanceof HttpAsyncClient)) {
-            throw new \LogicException('Client must be an instance of Psr\\Http\\Client\\ClientInterface or Http\\Client\\HttpAsyncClient');
+            throw new \LogicException(sprintf('Client must be an instance of %s or %s', ClientInterface::class, HttpAsyncClient::class));
         }
 
         $this->httpClient = $client;
diff --git a/src/PluginClient.php b/src/PluginClient.php
index 696d3ef..a3a4023 100644
--- a/src/PluginClient.php
+++ b/src/PluginClient.php
@@ -60,7 +60,7 @@ public function __construct($client, array $plugins = [], array $options = [])
         } elseif ($client instanceof ClientInterface) {
             $this->client = new EmulatedHttpAsyncClient($client);
         } else {
-            throw new \RuntimeException('Client must be an instance of Psr\\Http\\Client\\ClientInterface or Http\\Client\\HttpAsyncClient');
+            throw new \LogicException(sprintf('Client must be an instance of %s or %s', ClientInterface::class, HttpAsyncClient::class));
         }
 
         $this->plugins = $plugins;