diff --git a/src/main/java/com/rabbitmq/stream/impl/StreamEnvironmentBuilder.java b/src/main/java/com/rabbitmq/stream/impl/StreamEnvironmentBuilder.java
index 908fdae0ee..a411c2ebfa 100644
--- a/src/main/java/com/rabbitmq/stream/impl/StreamEnvironmentBuilder.java
+++ b/src/main/java/com/rabbitmq/stream/impl/StreamEnvironmentBuilder.java
@@ -99,7 +99,9 @@ private static URI toUri(String uriString) {
       }
       return uri;
     } catch (URISyntaxException e) {
-      throw new IllegalArgumentException("Invalid URI: " + uriString, e);
+      throw new IllegalArgumentException(
+          "Invalid URI syntax (" + e.getReason() + " at index " + e.getIndex() + ")"
+      );
     }
   }
 
diff --git a/src/main/java/com/rabbitmq/stream/oauth2/HttpTokenRequester.java b/src/main/java/com/rabbitmq/stream/oauth2/HttpTokenRequester.java
index 27db441a4d..232e8ccf57 100644
--- a/src/main/java/com/rabbitmq/stream/oauth2/HttpTokenRequester.java
+++ b/src/main/java/com/rabbitmq/stream/oauth2/HttpTokenRequester.java
@@ -66,7 +66,9 @@ public HttpTokenRequester(
     try {
       this.tokenEndpointUri = new URI(tokenEndpointUri);
     } catch (URISyntaxException e) {
-      throw new IllegalArgumentException("Error in URI: " + tokenEndpointUri);
+      throw new IllegalArgumentException(
+          "Invalid URI syntax (" + e.getReason() + " at index " + e.getIndex() + ")"
+      );
     }
     this.clientId = clientId;
     this.clientSecret = clientSecret;