diff --git a/CHANGELOG.md b/CHANGELOG.md
index e288665de8..ac1be3c740 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -71,6 +71,8 @@ For instructions on upgrading to newer versions, visit
 
 ### Resolved Issues
 
+* \#1680 Polymorphic relations now use `*_type` keys in lookup queries.
+
 * \#1676 Allow eager loading to work as a default scope.
 
 * \#1665/#1672 Expand complex criteria in nested criteria selectors, like
diff --git a/lib/mongoid/relations/builders/referenced/many.rb b/lib/mongoid/relations/builders/referenced/many.rb
index 7aacfa6693..511ecbbba9 100644
--- a/lib/mongoid/relations/builders/referenced/many.rb
+++ b/lib/mongoid/relations/builders/referenced/many.rb
@@ -17,7 +17,7 @@ class Many < Builder
           def build(type = nil)
             return object unless query?
             return [] if object.is_a?(Array)
-            crit = metadata.criteria(Conversions.flag(object, metadata))
+            crit = metadata.criteria(Conversions.flag(object, metadata), base.class)
             IdentityMap.get(crit.klass, crit.selector) || crit
           end
         end
diff --git a/lib/mongoid/relations/builders/referenced/many_to_many.rb b/lib/mongoid/relations/builders/referenced/many_to_many.rb
index 784a355045..1034c94fdf 100644
--- a/lib/mongoid/relations/builders/referenced/many_to_many.rb
+++ b/lib/mongoid/relations/builders/referenced/many_to_many.rb
@@ -17,7 +17,7 @@ class ManyToMany < Builder
           def build(type = nil)
             return object.try(:dup) unless query?
             ids = object || []
-            crit = metadata.criteria(ids)
+            crit = metadata.criteria(ids, base.class)
             IdentityMap.get(crit.klass, ids) || crit
           end
 
diff --git a/lib/mongoid/relations/builders/referenced/one.rb b/lib/mongoid/relations/builders/referenced/one.rb
index 8139908888..8c57ee9f8d 100644
--- a/lib/mongoid/relations/builders/referenced/one.rb
+++ b/lib/mongoid/relations/builders/referenced/one.rb
@@ -17,7 +17,7 @@ class One < Builder
           def build(type = nil)
             return object unless query?
             return nil if base.new_record?
-            metadata.criteria(Conversions.flag(object, metadata)).from_map_or_db
+            metadata.criteria(Conversions.flag(object, metadata), base.class).from_map_or_db
           end
         end
       end
diff --git a/lib/mongoid/relations/metadata.rb b/lib/mongoid/relations/metadata.rb
index 3b2ef212ae..88c9ca14c4 100644
--- a/lib/mongoid/relations/metadata.rb
+++ b/lib/mongoid/relations/metadata.rb
@@ -135,11 +135,12 @@ def constraint
       #   metadata.criteria([ id_one, id_two ])
       #
       # @param [ Object ] object The foreign key used for the query.
+      # @param [ Class ] type The base class.
       #
       # @return [ Criteria ] The criteria.
       #
       # @since 2.1.0
-      def criteria(object, type = nil)
+      def criteria(object, type)
         query = relation.criteria(self, object, type)
         order ? query.order_by(order) : query
       end
diff --git a/lib/mongoid/relations/referenced/many.rb b/lib/mongoid/relations/referenced/many.rb
index 22209751b9..d9d3b02671 100644
--- a/lib/mongoid/relations/referenced/many.rb
+++ b/lib/mongoid/relations/referenced/many.rb
@@ -389,7 +389,7 @@ def collection
         #
         # @since 2.0.0.beta.1
         def criteria
-          Many.criteria(metadata, Conversions.flag(base.id, metadata))
+          Many.criteria(metadata, Conversions.flag(base.id, metadata), base.class)
         end
 
         # Perform the necessary cascade operations for documents that just got
@@ -536,7 +536,11 @@ def builder(base, meta, object)
           #
           # @since 2.1.0
           def criteria(metadata, object, type = nil)
-            metadata.klass.where(metadata.foreign_key => object)
+            crit = metadata.klass.where(metadata.foreign_key => object)
+            if metadata.polymorphic?
+              crit = crit.where(metadata.type => type.name)
+            end
+            crit
           end
 
           # Eager load the relation based on the criteria.
diff --git a/lib/mongoid/relations/referenced/one.rb b/lib/mongoid/relations/referenced/one.rb
index 369640d32d..3373f18cb2 100644
--- a/lib/mongoid/relations/referenced/one.rb
+++ b/lib/mongoid/relations/referenced/one.rb
@@ -122,7 +122,11 @@ def builder(base, meta, object)
           #
           # @since 2.1.0
           def criteria(metadata, object, type = nil)
-            metadata.klass.where(metadata.foreign_key => object)
+            crit = metadata.klass.where(metadata.foreign_key => object)
+            if metadata.polymorphic?
+              crit = crit.where(metadata.type => type.name)
+            end
+            crit
           end
 
           # Get the criteria that is used to eager load a relation of this
diff --git a/lib/mongoid/relations/synchronization.rb b/lib/mongoid/relations/synchronization.rb
index 90667d1db0..d2947c0247 100644
--- a/lib/mongoid/relations/synchronization.rb
+++ b/lib/mongoid/relations/synchronization.rb
@@ -61,7 +61,7 @@ def synced?(foreign_key)
       #
       # @since 2.2.1
       def remove_inverse_keys(meta)
-        meta.criteria(send(meta.foreign_key)).pull(meta.inverse_foreign_key, id)
+        meta.criteria(send(meta.foreign_key), self.class).pull(meta.inverse_foreign_key, id)
       end
 
       # Update the inverse keys for the relation.
@@ -91,10 +91,10 @@ def update_inverse_keys(meta)
           end
 
           unless adds.empty?
-            meta.criteria(adds).add_to_set(meta.inverse_foreign_key, id)
+            meta.criteria(adds, self.class).add_to_set(meta.inverse_foreign_key, id)
           end
           unless subs.empty?
-            meta.criteria(subs).pull(meta.inverse_foreign_key, id)
+            meta.criteria(subs, self.class).pull(meta.inverse_foreign_key, id)
           end
         end
       end
diff --git a/spec/mongoid/relations/referenced/many_spec.rb b/spec/mongoid/relations/referenced/many_spec.rb
index b8e3c4be8c..7ca874c444 100644
--- a/spec/mongoid/relations/referenced/many_spec.rb
+++ b/spec/mongoid/relations/referenced/many_spec.rb
@@ -1598,6 +1598,45 @@
     end
   end
 
+  describe ".criteria" do
+
+    let(:id) do
+      BSON::ObjectId.new
+    end
+
+    context "when the relation is polymorphic" do
+
+      let(:metadata) do
+        Movie.relations["ratings"]
+      end
+
+      let(:criteria) do
+        described_class.criteria(metadata, id, Movie)
+      end
+
+      it "includes the type in the criteria" do
+        criteria.selector.should eq(
+          { "ratable_id" => id, "ratable_type" => "Movie" }
+        )
+      end
+    end
+
+    context "when the relation is not polymorphic" do
+
+      let(:metadata) do
+        Person.relations["posts"]
+      end
+
+      let(:criteria) do
+        described_class.criteria(metadata, id, Person)
+      end
+
+      it "does not include the type in the criteria" do
+        criteria.selector.should eq({ "person_id" => id })
+      end
+    end
+  end
+
   describe "#delete" do
 
     let!(:person) do
diff --git a/spec/mongoid/relations/referenced/one_spec.rb b/spec/mongoid/relations/referenced/one_spec.rb
index fc615cdf2f..6952fc3ba6 100644
--- a/spec/mongoid/relations/referenced/one_spec.rb
+++ b/spec/mongoid/relations/referenced/one_spec.rb
@@ -958,6 +958,45 @@
     end
   end
 
+  describe ".criteria" do
+
+    let(:id) do
+      BSON::ObjectId.new
+    end
+
+    context "when the relation is polymorphic" do
+
+      let(:metadata) do
+        Book.relations["rating"]
+      end
+
+      let(:criteria) do
+        described_class.criteria(metadata, id, Book)
+      end
+
+      it "includes the type in the criteria" do
+        criteria.selector.should eq(
+          { "ratable_id" => id, "ratable_type" => "Book" }
+        )
+      end
+    end
+
+    context "when the relation is not polymorphic" do
+
+      let(:metadata) do
+        Person.relations["game"]
+      end
+
+      let(:criteria) do
+        described_class.criteria(metadata, id, Person)
+      end
+
+      it "does not include the type in the criteria" do
+        criteria.selector.should eq({ "person_id" => id })
+      end
+    end
+  end
+
   describe ".eager_load" do
 
     before do