diff --git a/api/src/main/java/io/kafbat/ui/serdes/builtin/ProtobufFileSerde.java b/api/src/main/java/io/kafbat/ui/serdes/builtin/ProtobufFileSerde.java
index 618c711b1..9b78cc7b2 100644
--- a/api/src/main/java/io/kafbat/ui/serdes/builtin/ProtobufFileSerde.java
+++ b/api/src/main/java/io/kafbat/ui/serdes/builtin/ProtobufFileSerde.java
@@ -112,7 +112,7 @@ void configure(Configuration configuration) {
         && configuration.defaultKeyMessageDescriptor() == null
         && configuration.messageDescriptorMap().isEmpty()
         && configuration.keyMessageDescriptorMap().isEmpty()) {
-      throw new ValidationException("Neither default, not per-topic descriptors defined for " + name() + " serde");
+      throw new ValidationException("Neither default, nor per-topic descriptors defined for " + name() + " serde");
     }
     this.defaultMessageDescriptor = configuration.defaultMessageDescriptor();
     this.defaultKeyMessageDescriptor = configuration.defaultKeyMessageDescriptor();