diff --git a/cygnus-ngsi/src/main/java/com/telefonica/iot/cygnus/sinks/NGSIMongoSink.java b/cygnus-ngsi/src/main/java/com/telefonica/iot/cygnus/sinks/NGSIMongoSink.java
index c81b916f8..fe9f81823 100644
--- a/cygnus-ngsi/src/main/java/com/telefonica/iot/cygnus/sinks/NGSIMongoSink.java
+++ b/cygnus-ngsi/src/main/java/com/telefonica/iot/cygnus/sinks/NGSIMongoSink.java
@@ -235,17 +235,19 @@ private void persistAggregation(NGSIGenericAggregator aggregator) throws CygnusP
             JsonElement attType;
             if (rowAttrPersistence) {
                 attType = aggregator.getAggregation().get(NGSIConstants.ATTR_TYPE).get(i);
-                if ( (attType != null) &&
-                     (attType.toString().contains("ISO8601") ||
-                      attType.toString().contains("DateTime")) ) {
+                if ( (attType != null &&
+                      attType.isJsonPrimitive()) &&
+                     (attType.getAsString().equals("ISO8601") ||
+                      attType.getAsString().equals("DateTime")) ) {
                     basicDBObject = castDate(NGSIConstants.ATTR_VALUE, basicDBObject);
                 }
             } else {
                 for (String key : basicDBObject.keySet()) {
                     attType = aggregator.getAggregation().get(key + NGSIConstants.AUTOGENERATED_ATTR_TYPE).get(i);
-                    if ( (attType != null) &&
-                         (attType.toString().contains("ISO8601") ||
-                          attType.toString().contains("DateTime")) ) {
+                    if ( (attType != null &&
+                          attType.isJsonPrimitive()) &&
+                         (attType.getAsString().equals("ISO8601") ||
+                          attType.getAsString().equals("DateTime")) ) {
                         basicDBObject = castDate(key, basicDBObject);
                     }
                 }