Index: django/db/models/options.py
===================================================================
--- django/db/models/options.py	(revision 6780)
+++ django/db/models/options.py	(working copy)
@@ -152,7 +152,7 @@
             rel_objs = []
             for klass in get_models():
                 for f in klass._meta.fields:
-                    if f.rel and self == f.rel.to._meta:
+                    if f.rel and not isinstance(f.rel.to, str) and self == f.rel.to._meta:
                         rel_objs.append(RelatedObject(f.rel.to, klass, f))
             self._all_related_objects = rel_objs
             return rel_objs
@@ -186,7 +186,7 @@
             rel_objs = []
             for klass in get_models():
                 for f in klass._meta.many_to_many:
-                    if f.rel and self == f.rel.to._meta:
+                    if f.rel and not isinstance(f.rel.to, str) and self == f.rel.to._meta:
                         rel_objs.append(RelatedObject(f.rel.to, klass, f))
             if app_cache_ready():
                 self._all_related_many_to_many_objects = rel_objs
Index: django/core/management/validation.py
===================================================================
--- django/core/management/validation.py	(revision 6780)
+++ django/core/management/validation.py	(working copy)
@@ -72,10 +72,14 @@
             # Check to see if the related field will clash with any
             # existing fields, m2m fields, m2m related objects or related objects
             if f.rel:
-                rel_opts = f.rel.to._meta
                 if f.rel.to not in models.get_models():
-                    e.add(opts, "'%s' has relation with model %s, which has not been installed" % (f.name, rel_opts.object_name))
+                    e.add(opts, "'%s' has relation with model %s, which has not been installed" % (f.name, f.rel.to))
+                # it is a string and we could not find the model it refers to
+                # so skip the next section
+                if isinstance(f.rel.to, (str, unicode)):
+                    continue
 
+                rel_opts = f.rel.to._meta
                 rel_name = RelatedObject(f.rel.to, cls, f).get_accessor_name()
                 rel_query_name = f.related_query_name()
                 for r in rel_opts.fields:
@@ -103,10 +104,14 @@
         for i, f in enumerate(opts.many_to_many):
             # Check to see if the related m2m field will clash with any
             # existing fields, m2m fields, m2m related objects or related objects
-            rel_opts = f.rel.to._meta
             if f.rel.to not in models.get_models():
-                e.add(opts, "'%s' has m2m relation with model %s, which has not been installed" % (f.name, rel_opts.object_name))
+                e.add(opts, "'%s' has m2m relation with model %s, which has not been installed" % (f.name, f.rel.to))
+                # it is a string and we could not find the model it refers to
+                # so skip the next section
+                if isinstance(f.rel.to, (str, unicode)):
+                    continue
 
+            rel_opts = f.rel.to._meta
             rel_name = RelatedObject(f.rel.to, cls, f).get_accessor_name()
             rel_query_name = f.related_query_name()
             # If rel_name is none, there is no reverse accessor.
Index: tests/modeltests/invalid_models/models.py
===================================================================
--- tests/modeltests/invalid_models/models.py	(revision 6780)
+++ tests/modeltests/invalid_models/models.py	(working copy)
@@ -108,6 +108,10 @@
     colour = models.CharField(max_length=5)
     model = models.ForeignKey(Model)
 
+class MissingRelations(models.Model):
+    rel1 = models.ForeignKey("Rel1")
+    rel2 = models.ManyToManyField("Rel2")
+
 model_errors = """invalid_models.fielderrors: "charfield": CharFields require a "max_length" attribute.
 invalid_models.fielderrors: "decimalfield": DecimalFields require a "decimal_places" attribute.
 invalid_models.fielderrors: "decimalfield": DecimalFields require a "max_digits" attribute.
@@ -191,4 +195,6 @@
 invalid_models.selfclashm2m: Accessor for m2m field 'm2m_4' clashes with related m2m field 'SelfClashM2M.selfclashm2m_set'. Add a related_name argument to the definition for 'm2m_4'.
 invalid_models.selfclashm2m: Reverse query name for m2m field 'm2m_3' clashes with field 'SelfClashM2M.selfclashm2m'. Add a related_name argument to the definition for 'm2m_3'.
 invalid_models.selfclashm2m: Reverse query name for m2m field 'm2m_4' clashes with field 'SelfClashM2M.selfclashm2m'. Add a related_name argument to the definition for 'm2m_4'.
+invalid_models.missingrelations: 'rel2' has m2m relation with model Rel2, which has not been installed
+invalid_models.missingrelations: 'rel1' has relation with model Rel1, which has not been installed
 """