diff --git a/json_merger/comparator.py b/json_merger/comparator.py
index c4fce06..c56446a 100644
--- a/json_merger/comparator.py
+++ b/json_merger/comparator.py
@@ -105,16 +105,25 @@ class PrimaryKeyComparator(BaseComparator):
     primary_key_fields = ['pk']
     normalization_functions = {}
 
-    def _have_field_equal(self, obj1, obj2, field):
+    def _get_compared_objects_at_field_path(self, obj1, obj2, field):
         key_path = tuple(k for k in field.split('.') if k)
         o1 = get_obj_at_key_path(obj1, key_path, NOTHING)
         o2 = get_obj_at_key_path(obj2, key_path, NOTHING)
+        return o1, o2
+
+    def _have_field_equal(self, obj1, obj2, field):
+        o1, o2 = self._get_compared_objects_at_field_path(obj1, obj2, field)
         if o1 == NOTHING or o2 == NOTHING:
             return False
 
         fn = self.normalization_functions.get(field, lambda x: x)
         return fn(o1) == fn(o2)
 
+    def _are_fields_nothing(self, obj1, obj2, field):
+        o1, o2 = self._get_compared_objects_at_field_path(obj1, obj2, field)
+        if o1 == NOTHING or o2 == NOTHING:
+            return True
+
     def equal(self, obj1, obj2):
         if obj1 == obj2:
             return True
@@ -124,7 +133,11 @@ def equal(self, obj1, obj2):
                 field_set = [field_set]
             checks = [self._have_field_equal(obj1, obj2, field)
                       for field in field_set]
-            if all(checks):
+            are_all_fields_nothing = [
+                self._are_fields_nothing(obj1, obj2, field)
+                for field in field_set
+            ]
+            if all(checks) and not all(are_all_fields_nothing):
                 return True
 
         return False