diff --git a/oauth2/oauth2-core/src/main/java/org/springframework/security/oauth2/core/ClaimAccessor.java b/oauth2/oauth2-core/src/main/java/org/springframework/security/oauth2/core/ClaimAccessor.java
index 09e253ebb3..46256b58d3 100644
--- a/oauth2/oauth2-core/src/main/java/org/springframework/security/oauth2/core/ClaimAccessor.java
+++ b/oauth2/oauth2-core/src/main/java/org/springframework/security/oauth2/core/ClaimAccessor.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -107,7 +107,7 @@ public interface ClaimAccessor {
 		}
 		Object claimValue = getClaims().get(claim);
 		Instant convertedValue = ClaimConversionService.getSharedInstance().convert(claimValue, Instant.class);
-		Assert.isTrue(convertedValue != null,
+		Assert.notNull(convertedValue,
 				() -> "Unable to convert claim '" + claim + "' of type '" + claimValue.getClass() + "' to Instant.");
 		return convertedValue;
 	}
@@ -123,7 +123,7 @@ public interface ClaimAccessor {
 		}
 		Object claimValue = getClaims().get(claim);
 		URL convertedValue = ClaimConversionService.getSharedInstance().convert(claimValue, URL.class);
-		Assert.isTrue(convertedValue != null,
+		Assert.notNull(convertedValue,
 				() -> "Unable to convert claim '" + claim + "' of type '" + claimValue.getClass() + "' to URL.");
 		return convertedValue;
 	}
@@ -148,7 +148,7 @@ public interface ClaimAccessor {
 		Object claimValue = getClaims().get(claim);
 		Map<String, Object> convertedValue = (Map<String, Object>) ClaimConversionService.getSharedInstance()
 			.convert(claimValue, sourceDescriptor, targetDescriptor);
-		Assert.isTrue(convertedValue != null,
+		Assert.notNull(convertedValue,
 				() -> "Unable to convert claim '" + claim + "' of type '" + claimValue.getClass() + "' to Map.");
 		return convertedValue;
 	}
@@ -173,7 +173,7 @@ public interface ClaimAccessor {
 		Object claimValue = getClaims().get(claim);
 		List<String> convertedValue = (List<String>) ClaimConversionService.getSharedInstance()
 			.convert(claimValue, sourceDescriptor, targetDescriptor);
-		Assert.isTrue(convertedValue != null,
+		Assert.notNull(convertedValue,
 				() -> "Unable to convert claim '" + claim + "' of type '" + claimValue.getClass() + "' to List.");
 		return convertedValue;
 	}
diff --git a/oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/JoseHeader.java b/oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/JoseHeader.java
index f40fb09a55..3b749fe395 100644
--- a/oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/JoseHeader.java
+++ b/oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/JoseHeader.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -353,7 +353,7 @@ class JoseHeader {
 
 		private static URL convertAsURL(String header, String value) {
 			URL convertedValue = ClaimConversionService.getSharedInstance().convert(value, URL.class);
-			Assert.isTrue(convertedValue != null,
+			Assert.notNull(convertedValue,
 					() -> "Unable to convert header '" + header + "' of type '" + value.getClass() + "' to URL.");
 			return convertedValue;
 		}