diff --git a/debezium-operator-api/src/main/java/io/debezium/operator/api/config/ConfigMapping.java b/debezium-operator-api/src/main/java/io/debezium/operator/api/config/ConfigMapping.java
index 28d0ab1..613eb18 100644
--- a/debezium-operator-api/src/main/java/io/debezium/operator/api/config/ConfigMapping.java
+++ b/debezium-operator-api/src/main/java/io/debezium/operator/api/config/ConfigMapping.java
@@ -105,10 +105,9 @@ record NamedItem(String name, ConfigMappable item) {
 
         named.stream()
                 .map(NamedItem::name)
-                .reduce((x, y) -> String.join(","))
+                .reduce((x, y) -> x + "," + y)
                 .ifPresent(names -> put(key, names));
 
-
         named.forEach(item -> putAll(key + "." + item.name, item.item));
         return this;
     }
diff --git a/debezium-operator-api/src/test/java/io/debezium/operator/api/config/ConfigMappingTest.java b/debezium-operator-api/src/test/java/io/debezium/operator/api/config/ConfigMappingTest.java
index 9114bd0..8d12159 100644
--- a/debezium-operator-api/src/test/java/io/debezium/operator/api/config/ConfigMappingTest.java
+++ b/debezium-operator-api/src/test/java/io/debezium/operator/api/config/ConfigMappingTest.java
@@ -83,7 +83,7 @@ void shouldAddList() {
 
         config.putList("transforms", transformations, "Reroute");
 
-        assertThat(config.getAsMap()).containsEntry("transforms", "");
+        assertThat(config.getAsMap()).containsEntry("transforms", "Reroute0,Reroute1");
         assertThat(config.getAsMap()).containsEntry("transforms.Reroute0.type", "io.debezium.transforms.ByLogicalTableRouter");
         assertThat(config.getAsMap()).containsEntry("transforms.Reroute0.negate", "false");
         assertThat(config.getAsMap()).containsEntry("transforms.Reroute1.type", "io.debezium.transforms.ByLogicalTableRouter");
@@ -93,7 +93,7 @@ void shouldAddList() {
                 "transforms.Reroute0.type=io.debezium.transforms.ByLogicalTableRouter\n" +
                 "transforms.Reroute1.negate=true\n" +
                 "transforms.Reroute1.type=io.debezium.transforms.ByLogicalTableRouter\n" +
-                "transforms=");
+                "transforms=Reroute0,Reroute1");
     }
 
     @Test