diff --git a/src/main/java/io/frictionlessdata/datapackage/resource/AbstractResource.java b/src/main/java/io/frictionlessdata/datapackage/resource/AbstractResource.java
index dd53e73..a51b5aa 100644
--- a/src/main/java/io/frictionlessdata/datapackage/resource/AbstractResource.java
+++ b/src/main/java/io/frictionlessdata/datapackage/resource/AbstractResource.java
@@ -411,6 +411,9 @@ public void checkRelations(Package pkg) {
                                 Map<String, String> fieldMapping = fk.getForeignKey().getFieldMapping();
                                 String refFieldName = fieldMapping.get(key);
                                 Object fkVal = row.get(key);
+                                if (fkVal == null) {
+                                    continue;
+                                }
                                 boolean found = false;
 
                                 for (Object refRow : refData) {