diff --git a/src/Assert/HMACOutputLengthTrait.php b/src/Assert/HMACOutputLengthTrait.php
index 6b1bbe55..f2c292d2 100644
--- a/src/Assert/HMACOutputLengthTrait.php
+++ b/src/Assert/HMACOutputLengthTrait.php
@@ -4,6 +4,7 @@
 
 namespace SimpleSAML\XMLSecurity\Assert;
 
+use SimpleSAML\Assert\AssertionFailedException;
 use SimpleSAML\XML\Exception\SchemaViolationException;
 use SimpleSAML\XMLSecurity\Exception\ProtocolViolationException;