diff --git a/extensions/smallrye-graphql/deployment/src/test/java/io/quarkus/smallrye/graphql/deployment/AbstractGraphQLTest.java b/extensions/smallrye-graphql/deployment/src/test/java/io/quarkus/smallrye/graphql/deployment/AbstractGraphQLTest.java
index 382b64bceb66d..a90bf35a174de 100644
--- a/extensions/smallrye-graphql/deployment/src/test/java/io/quarkus/smallrye/graphql/deployment/AbstractGraphQLTest.java
+++ b/extensions/smallrye-graphql/deployment/src/test/java/io/quarkus/smallrye/graphql/deployment/AbstractGraphQLTest.java
@@ -67,11 +67,13 @@ protected static String getPropertyAsString() {
 
     protected static String getPropertyAsString(Map<String, String> otherProperties) {
         try {
+            Properties p = new Properties();
+            p.putAll(PROPERTIES);
             StringWriter writer = new StringWriter();
             if (otherProperties != null) {
-                PROPERTIES.putAll(otherProperties);
+                p.putAll(otherProperties);
             }
-            PROPERTIES.store(writer, "Test Properties");
+            p.store(writer, "Test Properties");
             return writer.toString();
         } catch (IOException ex) {
             throw new RuntimeException(ex);