diff --git a/src/main/java/org/onap/dcaegen2/services/pmmapper/model/MeasFilterConfig.java b/src/main/java/org/onap/dcaegen2/services/pmmapper/model/MeasFilterConfig.java
index 0f1aaa9..a7d211f 100644
--- a/src/main/java/org/onap/dcaegen2/services/pmmapper/model/MeasFilterConfig.java
+++ b/src/main/java/org/onap/dcaegen2/services/pmmapper/model/MeasFilterConfig.java
@@ -33,6 +33,7 @@
 @NoArgsConstructor
 public class MeasFilterConfig {
 
+  @GSONRequired
   @SerializedName("filters")
   public List<Filter> filters;
 
diff --git a/src/main/java/org/onap/dcaegen2/services/pmmapper/utils/RequiredFieldDeserializer.java b/src/main/java/org/onap/dcaegen2/services/pmmapper/utils/RequiredFieldDeserializer.java
index e956398..258b831 100644
--- a/src/main/java/org/onap/dcaegen2/services/pmmapper/utils/RequiredFieldDeserializer.java
+++ b/src/main/java/org/onap/dcaegen2/services/pmmapper/utils/RequiredFieldDeserializer.java
@@ -25,8 +25,13 @@
 import com.google.gson.JsonElement;
 import com.google.gson.JsonParseException;
 
+import lombok.NonNull;
+
 import java.lang.reflect.Field;
 import java.lang.reflect.Type;
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Stream;
 
 
 /**
@@ -38,20 +43,35 @@
     @Override
     public T deserialize(JsonElement jsonElement, Type type, JsonDeserializationContext jsonDeserializationContext) throws JsonParseException {
         T obj = new Gson().fromJson(jsonElement, type);
-        for (Field field : obj.getClass().getDeclaredFields()) {
-            if (field.getAnnotation(GSONRequired.class) != null) {
-                field.setAccessible(true);
-                try {
-                    if (field.get(obj) == null) {
-                        throw new JsonParseException(String.format("Field: '%s', is required but not found.", field.getName()));
-                    }
-                } catch (Exception exception) {
-                    throw new JsonParseException("Failed to check fields.", exception);
-                }
+        validateRequiredFields(obj.getClass().getDeclaredFields(), obj);
+        return obj;
+    }
+
+    private void validateRequiredFields(@NonNull Field[] fields, @NonNull Object pojo) {
+        if (pojo instanceof List) {
+            final List<?> pojoList = (List<?>) pojo;
+            for (final Object pojoListPojo : pojoList) {
+                validateRequiredFields(pojoListPojo.getClass().getDeclaredFields(), pojoListPojo);
             }
         }
 
-        return obj;
+        Stream.of(fields)
+            .filter(field -> field.getAnnotation(GSONRequired.class) != null)
+            .forEach(field -> {
+                try {
+                    field.setAccessible(true);
+                    Object fieldObj = Optional.ofNullable(field.get(pojo))
+                        .orElseThrow(()-> new JsonParseException(
+                            String.format("Field '%s' in class '%s' is required but not found.",
+                            field.getName(), pojo.getClass().getSimpleName())));
+
+                    Field[] declaredFields = fieldObj.getClass().getDeclaredFields();
+                    validateRequiredFields(declaredFields, fieldObj);
+                }
+                catch (Exception exception) {
+                    throw new JsonParseException("Failed to check fields.", exception);
+                }
+            });
     }
 
 }
diff --git a/src/test/java/org/onap/dcaegen2/pmmapper/config/ConfigHandlerTests.java b/src/test/java/org/onap/dcaegen2/pmmapper/config/ConfigHandlerTests.java
index f6aa2a8..e2bb4f5 100644
--- a/src/test/java/org/onap/dcaegen2/pmmapper/config/ConfigHandlerTests.java
+++ b/src/test/java/org/onap/dcaegen2/pmmapper/config/ConfigHandlerTests.java
@@ -25,6 +25,8 @@
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.net.UnknownHostException;
+import java.util.HashMap;
+import java.util.Map;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
@@ -48,6 +50,8 @@
 import org.powermock.modules.junit4.PowerMockRunner;
 
 import com.google.gson.Gson;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
 
 import ch.qos.logback.classic.spi.ILoggingEvent;
 import ch.qos.logback.core.read.ListAppender;
@@ -114,8 +118,24 @@
 
     @Test
     public void mapper_parse_valid_json_missing_attributes() throws Exception {
-        when(sender.send(anyString())).thenReturn(getFileContents("incomplete_mapper_config.json"));
-        assertThrows(MapperConfigException.class, this::getMapperConfig);
+        Map<String,String> invalidConfigs = new HashMap<>();
+        invalidConfigs.put("streams_subscribes", "{}");
+        invalidConfigs.put("streams_publishes", "{}");
+        invalidConfigs.put("streams_publishes", null);
+        invalidConfigs.remove("streams_publishes");
+        invalidConfigs.put("pm-mapper-filter", null);
+        invalidConfigs.put("pm-mapper-filter", "{}");
+        invalidConfigs.put("pm-mapper-filter", "{ \"filters\": null},");
+        invalidConfigs.put("pm-mapper-filter", "{ \"filters\": [{\"pmDefVsn\": \"V9\"}] },");
+
+        invalidConfigs.forEach( (k,v) -> {
+            try {
+                when(sender.send(anyString())).thenReturn( getInvalidConfig(k,v));
+                assertThrows(MapperConfigException.class, this::getMapperConfig);
+            } catch (Exception e) {
+                e.printStackTrace();
+            }
+        });
     }
 
     private MapperConfig getMapperConfig()
@@ -136,4 +156,10 @@
         return fileAsString;
     }
 
+    private String getInvalidConfig(String validKey, String invalidValue) {
+        JsonObject invalidConfigJson = new JsonParser().parse(validMapperConfig).getAsJsonObject();
+        invalidConfigJson.addProperty(validKey, invalidValue);
+        return invalidConfigJson.toString();
+    }
+
 }
diff --git a/src/test/resources/incomplete_mapper_config.json b/src/test/resources/incomplete_mapper_config.json
deleted file mode 100644
index ed4ebd7..0000000
--- a/src/test/resources/incomplete_mapper_config.json
+++ /dev/null
@@ -1,24 +0,0 @@
-{
-    "_comment": "This mapper config is missing streams_subscribes",
-    "pm-mapper-filter": {
-        "filters": "{[]}"
-    },
-    "3GPP.schema.file": "{\"3GPP_Schema\":\"./etc/3GPP_relaxed_schema.xsd\"}",
-    "streams_subscribes": null,
-    "streams_publishes": {
-        "pm_mapper_handle_out": {
-            "type": "message_router",
-            "aaf_password": null,
-            "dmaap_info": {
-                "topic_url": "https://we-are-message-router.us:3905/events/some-topic",
-                "client_role": null,
-                "location": null,
-                "client_id": null
-            },
-            "aaf_username": null
-        }
-    },
-    "some parameter": "unauthenticated.PM_VES_OUTPUT",
-    "some field": "1",
-    "services_calls": {}
-}
\ No newline at end of file