diff --git a/django/core/management/validation.py b/django/core/management/validation.py
index ddf454ffad..554c59e856 100644
--- a/django/core/management/validation.py
+++ b/django/core/management/validation.py
@@ -80,6 +80,10 @@ def get_validation_errors(outfile, app=None):
                 if isinstance(f.rel.to, (str, unicode)):
                     continue
 
+                # Make sure the related field specified by a ForeignKey is unique
+                if not f.rel.to._meta.get_field(f.rel.field_name).unique:
+                    e.add(opts, "Field '%s' under model '%s' must have a unique=True constraint." % (f.rel.field_name, f.rel.to.__name__))
+
                 rel_opts = f.rel.to._meta
                 rel_name = RelatedObject(f.rel.to, cls, f).get_accessor_name()
                 rel_query_name = f.related_query_name()
diff --git a/tests/modeltests/invalid_models/models.py b/tests/modeltests/invalid_models/models.py
index 4957f768f7..8aa7678930 100644
--- a/tests/modeltests/invalid_models/models.py
+++ b/tests/modeltests/invalid_models/models.py
@@ -180,7 +180,27 @@ class AbstractRelationModel(models.Model):
 
 class UniqueM2M(models.Model):
     """ Model to test for unique ManyToManyFields, which are invalid. """
-    unique_people = models.ManyToManyField( Person, unique=True )
+    unique_people = models.ManyToManyField(Person, unique=True)
+
+class NonUniqueFKTarget1(models.Model):
+    """ Model to test for non-unique FK target in yet-to-be-defined model: expect an error """
+    tgt = models.ForeignKey('FKTarget', to_field='bad')
+
+class UniqueFKTarget1(models.Model):
+    """ Model to test for unique FK target in yet-to-be-defined model: expect no error """
+    tgt = models.ForeignKey('FKTarget', to_field='good')
+
+class FKTarget(models.Model):
+    bad = models.IntegerField()
+    good = models.IntegerField(unique=True)
+
+class NonUniqueFKTarget2(models.Model):
+    """ Model to test for non-unique FK target in previously seen model: expect an error """
+    tgt = models.ForeignKey(FKTarget, to_field='bad')
+
+class UniqueFKTarget2(models.Model):
+    """ Model to test for unique FK target in previously seen model: expect no error """
+    tgt = models.ForeignKey(FKTarget, to_field='good')
 
 
 model_errors = """invalid_models.fielderrors: "charfield": CharFields require a "max_length" attribute.
@@ -279,4 +299,6 @@ invalid_models.personselfrefm2mexplicit: Many-to-many fields with intermediate t
 invalid_models.abstractrelationmodel: 'fk1' has a relation with model AbstractModel, which has either not been installed or is abstract.
 invalid_models.abstractrelationmodel: 'fk2' has an m2m relation with model AbstractModel, which has either not been installed or is abstract.
 invalid_models.uniquem2m: ManyToManyFields cannot be unique.  Remove the unique argument on 'unique_people'.
+invalid_models.nonuniquefktarget1: Field 'bad' under model 'FKTarget' must have a unique=True constraint.
+invalid_models.nonuniquefktarget2: Field 'bad' under model 'FKTarget' must have a unique=True constraint.
 """