diff --git a/persistence/persistence-mybatis/src/main/java/org/cbioportal/persistence/mybatis/AlterationMyBatisRepository.java b/persistence/persistence-mybatis/src/main/java/org/cbioportal/persistence/mybatis/AlterationMyBatisRepository.java
index 47b861df951..a48b6476b59 100644
--- a/persistence/persistence-mybatis/src/main/java/org/cbioportal/persistence/mybatis/AlterationMyBatisRepository.java
+++ b/persistence/persistence-mybatis/src/main/java/org/cbioportal/persistence/mybatis/AlterationMyBatisRepository.java
@@ -36,8 +36,10 @@ public List<AlterationCountByGene> getSampleAlterationGeneCounts(Set<MolecularPr
             || (molecularProfileCaseIdentifiers == null || molecularProfileCaseIdentifiers.isEmpty())
             || allAlterationsExcludedDriverAnnotation(alterationFilter)
             || allAlterationsExcludedMutationStatus(alterationFilter)
-            || allAlterationsExcludedDriverTierAnnotation(alterationFilter)) {
-            return Collections.emptyList();
+            || allAlterationsExcludedDriverTierAnnotation(alterationFilter)
+        ) {
+            // We want a mutable empty list:
+            return new ArrayList<>();
         }
 
         Set<String> molecularProfileIds = molecularProfileCaseIdentifiers.stream()