memoizeit

diff --git a/src/main/java/br/ufrgs/inf/prosoft/memoizeit/OccurrenceConcrete.java b/src/main/java/br/ufrgs/inf/prosoft/memoizeit/OccurrenceConcrete.java
index c21222d..0c910f6 100644
--- a/src/main/java/br/ufrgs/inf/prosoft/memoizeit/OccurrenceConcrete.java
+++ b/src/main/java/br/ufrgs/inf/prosoft/memoizeit/OccurrenceConcrete.java
@@ -59,7 +59,7 @@ public class OccurrenceConcrete extends Occurrence {
             String parameterType = parameter.getType();
             if (parameter.getData() instanceof Collection) {
                 Collection collection = (Collection) parameter.getData();
-                if (collection.stream().findAny().get() instanceof Map) {
+                if (!collection.isEmpty() && collection.stream().findAny().get() instanceof Map) {
                     Collection<Map<String, Object>> cast = collection;
                     cast.forEach(map -> removeUnusedFields(map, parameterType, methodNode));
                 }