diff --git a/src/Prometheus/Exception/MetricNotFoundException.php b/src/Prometheus/Exception/MetricNotFoundException.php
index 73bee83..28d1b72 100644
--- a/src/Prometheus/Exception/MetricNotFoundException.php
+++ b/src/Prometheus/Exception/MetricNotFoundException.php
@@ -2,11 +2,11 @@
 
 namespace Prometheus\Exception;
 
-use Exception;
+use RuntimeException;
 
 /**
  * Exception thrown if a metric can't be found in the CollectorRegistry.
  */
-class MetricNotFoundException extends Exception
+class MetricNotFoundException extends RuntimeException
 {
 }