diff --git a/src/Assert/Assert.php b/src/Assert/Assert.php
new file mode 100644
index 00000000..0d8f6b94
--- /dev/null
+++ b/src/Assert/Assert.php
@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\XMLSecurity\Assert;
+
+use SimpleSAML\XML\Assert\Assert as BaseAssert;
+
+/**
+ * SimpleSAML\XMLSecurity\Assert\Assert wrapper class
+ *
+ * @package simplesamlphp/xml-security
+ */
+class Assert extends BaseAssert
+{
+}
diff --git a/src/CryptoEncoding/PEMBundle.php b/src/CryptoEncoding/PEMBundle.php
index 5ca7a544..a814bc8f 100644
--- a/src/CryptoEncoding/PEMBundle.php
+++ b/src/CryptoEncoding/PEMBundle.php
@@ -8,7 +8,7 @@
 use Countable;
 use IteratorAggregate;
 use LogicException;
-use SimpleSAML\Assert\Assert;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 use SimpleSAML\XMLSecurity\Exception\IOException;
 use UnexpectedValueException;
 
@@ -77,7 +77,7 @@ public static function fromString(string $str): self
         $pems = array_map(
             function ($match) {
                 $payload = preg_replace('/\s+/', '', $match[2]);
-                Assert::stringPlausibleBase64($payload);
+                Assert::validBase64($payload);
 
                 $data = base64_decode($payload, true);
                 if (empty($data)) {
diff --git a/src/XML/ds/AbstractKeyInfoType.php b/src/XML/ds/AbstractKeyInfoType.php
index d907c1ef..dadff6fc 100644
--- a/src/XML/ds/AbstractKeyInfoType.php
+++ b/src/XML/ds/AbstractKeyInfoType.php
@@ -5,11 +5,11 @@
 namespace SimpleSAML\XMLSecurity\XML\ds;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Exception\SchemaViolationException;
 use SimpleSAML\XML\ExtendableElementTrait;
 use SimpleSAML\XML\SerializableElementInterface;
 use SimpleSAML\XML\XsNamespace as NS;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 use SimpleSAML\XMLSecurity\Constants as C;
 use SimpleSAML\XMLSecurity\Exception\InvalidArgumentException;
 use SimpleSAML\XMLSecurity\XML\ds\AbstractDsElement;
diff --git a/src/XML/ds/DsObject.php b/src/XML/ds/DsObject.php
index 55f944be..592c11ec 100644
--- a/src/XML/ds/DsObject.php
+++ b/src/XML/ds/DsObject.php
@@ -5,12 +5,12 @@
 namespace SimpleSAML\XMLSecurity\XML\ds;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\ExtendableElementTrait;
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
 use SimpleSAML\XML\XsNamespace as NS;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 
 /**
  * Class representing a ds:Object element.
diff --git a/src/XML/ds/Manifest.php b/src/XML/ds/Manifest.php
index 171cae55..1c7adac0 100644
--- a/src/XML/ds/Manifest.php
+++ b/src/XML/ds/Manifest.php
@@ -5,12 +5,12 @@
 namespace SimpleSAML\XMLSecurity\XML\ds;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Constants as C;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\Exception\MissingElementException;
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 
 /**
  * Class representing a ds:Manifest element.
diff --git a/src/XML/ds/Reference.php b/src/XML/ds/Reference.php
index e645b485..91db0085 100644
--- a/src/XML/ds/Reference.php
+++ b/src/XML/ds/Reference.php
@@ -5,12 +5,12 @@
 namespace SimpleSAML\XMLSecurity\XML\ds;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\Exception\MissingElementException;
 use SimpleSAML\XML\Exception\TooManyElementsException;
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 
 use function array_pop;
 
diff --git a/src/XML/ds/Signature.php b/src/XML/ds/Signature.php
index 9211e5fd..e5da1f3d 100644
--- a/src/XML/ds/Signature.php
+++ b/src/XML/ds/Signature.php
@@ -5,12 +5,12 @@
 namespace SimpleSAML\XMLSecurity\XML\ds;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\Exception\MissingElementException;
 use SimpleSAML\XML\Exception\TooManyElementsException;
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 use SimpleSAML\XMLSecurity\Constants as C;
 
 use function array_pop;
diff --git a/src/XML/ds/SignatureProperties.php b/src/XML/ds/SignatureProperties.php
index ac0290ac..c0aeb7c8 100644
--- a/src/XML/ds/SignatureProperties.php
+++ b/src/XML/ds/SignatureProperties.php
@@ -5,13 +5,13 @@
 namespace SimpleSAML\XMLSecurity\XML\ds;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Constants as C;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\Exception\MissingElementException;
 use SimpleSAML\XML\Exception\SchemaViolationException;
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 
 /**
  * Class representing a ds:SignatureProperties element.
diff --git a/src/XML/ds/SignatureProperty.php b/src/XML/ds/SignatureProperty.php
index 1c31fd4c..3f07cedd 100644
--- a/src/XML/ds/SignatureProperty.php
+++ b/src/XML/ds/SignatureProperty.php
@@ -5,7 +5,6 @@
 namespace SimpleSAML\XMLSecurity\XML\ds;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\Exception\MissingElementException;
 use SimpleSAML\XML\Exception\SchemaViolationException;
@@ -13,6 +12,7 @@
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
 use SimpleSAML\XML\XsNamespace as NS;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 
 /**
  * Class representing a ds:SignatureProperty element.
diff --git a/src/XML/ds/SignatureValue.php b/src/XML/ds/SignatureValue.php
index 11176aac..cb51b850 100644
--- a/src/XML/ds/SignatureValue.php
+++ b/src/XML/ds/SignatureValue.php
@@ -5,11 +5,11 @@
 namespace SimpleSAML\XMLSecurity\XML\ds;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Base64ElementTrait;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 
 /**
  * Class representing a ds:SignatureValue element.
diff --git a/src/XML/ds/SignedInfo.php b/src/XML/ds/SignedInfo.php
index 658589ca..7fb621ae 100644
--- a/src/XML/ds/SignedInfo.php
+++ b/src/XML/ds/SignedInfo.php
@@ -5,13 +5,13 @@
 namespace SimpleSAML\XMLSecurity\XML\ds;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Constants as C;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\Exception\MissingElementException;
 use SimpleSAML\XML\Exception\TooManyElementsException;
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 use SimpleSAML\XMLSecurity\Exception\InvalidArgumentException;
 use SimpleSAML\XMLSecurity\XML\CanonicalizableElementInterface;
 use SimpleSAML\XMLSecurity\XML\CanonicalizableElementTrait;
diff --git a/src/XML/dsig11/KeyInfoReference.php b/src/XML/dsig11/KeyInfoReference.php
index fdc9526d..18382dd3 100644
--- a/src/XML/dsig11/KeyInfoReference.php
+++ b/src/XML/dsig11/KeyInfoReference.php
@@ -5,11 +5,11 @@
 namespace SimpleSAML\XMLSecurity\XML\dsig11;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\Exception\SchemaViolationException;
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 
 /**
  * Class representing a dsig11:KeyInfoReference element.
diff --git a/src/XML/xenc/AbstractEncryptedType.php b/src/XML/xenc/AbstractEncryptedType.php
index ad005c03..da8b702d 100644
--- a/src/XML/xenc/AbstractEncryptedType.php
+++ b/src/XML/xenc/AbstractEncryptedType.php
@@ -5,8 +5,8 @@
 namespace SimpleSAML\XMLSecurity\XML\xenc;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Exception\SchemaViolationException;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 use SimpleSAML\XMLSecurity\XML\ds\KeyInfo;
 
 /**
diff --git a/src/XML/xenc/AbstractEncryptionPropertiesType.php b/src/XML/xenc/AbstractEncryptionPropertiesType.php
index f425ade7..0c33620e 100644
--- a/src/XML/xenc/AbstractEncryptionPropertiesType.php
+++ b/src/XML/xenc/AbstractEncryptionPropertiesType.php
@@ -5,12 +5,12 @@
 namespace SimpleSAML\XMLSecurity\XML\xenc;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\Exception\MissingElementException;
 use SimpleSAML\XML\Exception\SchemaViolationException;
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 
 /**
  * Class representing <xenc:EncryptionPropertiesType>.
diff --git a/src/XML/xenc/AbstractEncryptionPropertyType.php b/src/XML/xenc/AbstractEncryptionPropertyType.php
index b6a2756b..f482617c 100644
--- a/src/XML/xenc/AbstractEncryptionPropertyType.php
+++ b/src/XML/xenc/AbstractEncryptionPropertyType.php
@@ -5,7 +5,6 @@
 namespace SimpleSAML\XMLSecurity\XML\xenc;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Constants as C;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\Exception\MissingElementException;
@@ -15,6 +14,7 @@
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
 use SimpleSAML\XML\XsNamespace as NS;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 
 /**
  * Class representing <xenc:EncryptionPropertyType>.
diff --git a/src/XML/xenc11/AbstractConcatKDFParamsType.php b/src/XML/xenc11/AbstractConcatKDFParamsType.php
index fd804962..441f9957 100644
--- a/src/XML/xenc11/AbstractConcatKDFParamsType.php
+++ b/src/XML/xenc11/AbstractConcatKDFParamsType.php
@@ -5,13 +5,13 @@
 namespace SimpleSAML\XMLSecurity\XML\xenc11;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\Exception\MissingElementException;
 use SimpleSAML\XML\Exception\SchemaViolationException;
 use SimpleSAML\XML\Exception\TooManyElementsException;
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 use SimpleSAML\XMLSecurity\XML\ds\DigestMethod;
 
 use function array_pop;
diff --git a/src/XML/xenc11/AbstractDerivedKeyType.php b/src/XML/xenc11/AbstractDerivedKeyType.php
index 5a1cd9ef..3db1febf 100644
--- a/src/XML/xenc11/AbstractDerivedKeyType.php
+++ b/src/XML/xenc11/AbstractDerivedKeyType.php
@@ -5,12 +5,12 @@
 namespace SimpleSAML\XMLSecurity\XML\xenc11;
 
 use DOMElement;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\XML\Exception\InvalidDOMElementException;
 use SimpleSAML\XML\Exception\SchemaViolationException;
 use SimpleSAML\XML\Exception\TooManyElementsException;
 use SimpleSAML\XML\SchemaValidatableElementInterface;
 use SimpleSAML\XML\SchemaValidatableElementTrait;
+use SimpleSAML\XMLSecurity\Assert\Assert;
 use SimpleSAML\XMLSecurity\XML\xenc\ReferenceList;
 
 use function array_pop;