diff --git a/private-rows-extensions/src/main/java/it/inaf/ia2/vollt/PrivateRowsQueryExecutor.java b/private-rows-extensions/src/main/java/it/inaf/ia2/vollt/PrivateRowsQueryExecutor.java
index 92a4943b77efb19e34c1c8f43d9b58c8fb5fcd73..b660db9cc3818547aa93f54923695aa85624bc2c 100644
--- a/private-rows-extensions/src/main/java/it/inaf/ia2/vollt/PrivateRowsQueryExecutor.java
+++ b/private-rows-extensions/src/main/java/it/inaf/ia2/vollt/PrivateRowsQueryExecutor.java
@@ -16,7 +16,7 @@ public class PrivateRowsQueryExecutor extends QueryExecutor {
             CustomJobOwner user = (CustomJobOwner) jobOwner;
             statement.execute("SET my.tap_groups = \"{"
                     + String.join(",", user.getGroups().stream()
-                            .map(g -> "'" + g.replace("'", "''") + "'")
+                            .map(g -> g.replace("'", "''"))
                             .collect(Collectors.toList()))
                     + "}\"");
         }
diff --git a/private-rows-extensions/src/test/java/it/inaf/ia2/vollt/PrivateRowsQueryExecutorTest.java b/private-rows-extensions/src/test/java/it/inaf/ia2/vollt/PrivateRowsQueryExecutorTest.java
index 491598acb79a6a7731a0516d36c40d2b5228bc4c..58443f78c4ae3c7f1cffc0989bbd0eebb7ab1baa 100644
--- a/private-rows-extensions/src/test/java/it/inaf/ia2/vollt/PrivateRowsQueryExecutorTest.java
+++ b/private-rows-extensions/src/test/java/it/inaf/ia2/vollt/PrivateRowsQueryExecutorTest.java
@@ -19,7 +19,7 @@ public class PrivateRowsQueryExecutorTest {
         Statement mockedStatement = mock(Statement.class);
         queryExecutor.executeQuery(mockedStatement, "", user);
 
-        verify(mockedStatement).execute(eq("SET my.tap_groups = \"{'group1','group2'}\""));
+        verify(mockedStatement).execute(eq("SET my.tap_groups = \"{group1,group2}\""));
 
         user = new CustomJobOwner("anonymous", Arrays.asList());
         queryExecutor.executeQuery(mockedStatement, "", user);