diff --git a/lib/baby_squeel/active_record.rb b/lib/baby_squeel/active_record.rb
index 4f71e53..3417c24 100644
--- a/lib/baby_squeel/active_record.rb
+++ b/lib/baby_squeel/active_record.rb
@@ -13,7 +13,8 @@ def sifter(name, &block)
     module QueryMethods
       # Constructs Arel for ActiveRecord::Base#joins using the DSL.
       def joining(&block)
-        joins DSL.evaluate(unscoped, &block)
+        arel, binds = DSL.evaluate_joins(unscoped, &block)
+        joins(arel).tap { |s| s.bind_values += binds }
       end
 
       # Constructs Arel for ActiveRecord::Base#select using the DSL.
diff --git a/lib/baby_squeel/dsl.rb b/lib/baby_squeel/dsl.rb
index a0b41f0..e23c766 100644
--- a/lib/baby_squeel/dsl.rb
+++ b/lib/baby_squeel/dsl.rb
@@ -4,16 +4,32 @@
 
 module BabySqueel
   class DSL < Table
-    # Evaluates a block in the context of a new DSL instance.
-    def self.evaluate(scope, &block)
-      new(scope).evaluate(&block)
-    end
+    class << self
+      # Evaluates a block and unwraps the nodes
+      def evaluate(scope, &block)
+        Nodes.unwrap evaluate!(scope, &block)
+      end
+
+      # Evaluates a block in the context of a DSL instance
+      def evaluate!(scope, &block)
+        new(scope).evaluate(&block)
+      end
+
+      # Evaluates a block specifically for a join. In this
+      # case, we'll return an array of Arel join nodes and
+      # a list of bind parameters.
+      def evaluate_joins(scope, &block)
+        dependency = evaluate!(scope, &block)._arel
+        join_arel = Nodes.unwrap(dependency._arel)
+        [join_arel, dependency.bind_values]
+      end
 
-    # Evaluates a block in the context of a new DSL instance
-    # and passes all arguments to the block.
-    def self.evaluate_sifter(scope, *args, &block)
-      evaluate scope do |root|
-        root.instance_exec(*args, &block)
+      # Evaluates a block in the context of a new DSL instance
+      # and passes all arguments to the block.
+      def evaluate_sifter(scope, *args, &block)
+        evaluate scope do |root|
+          root.instance_exec(*args, &block)
+        end
       end
     end
 
@@ -39,16 +55,16 @@ def sql(value)
 
     # Quotes a string and marks it as SQL
     def quoted(value)
-      sql @scope.connection.quote(value)
+      sql _scope.connection.quote(value)
     end
 
     # Evaluates a DSL block. If arity is given, this method
     # `yield` itself, rather than `instance_eval`.
     def evaluate(&block)
       if block.arity.zero?
-        Nodes.unwrap instance_eval(&block)
+        instance_eval(&block)
       else
-        Nodes.unwrap yield(self)
+        yield(self)
       end
     end
 
diff --git a/lib/baby_squeel/join_dependency.rb b/lib/baby_squeel/join_dependency.rb
index 869c93c..0c4ca2f 100644
--- a/lib/baby_squeel/join_dependency.rb
+++ b/lib/baby_squeel/join_dependency.rb
@@ -1,7 +1,10 @@
 module BabySqueel
   class JoinDependency
-    def initialize(scope, associations = [])
-      @scope = scope
+    attr_reader :bind_values
+
+    def initialize(table, associations = [])
+      @table = table
+      @bind_values = []
       @associations = associations
     end
 
@@ -10,9 +13,13 @@ def initialize(scope, associations = [])
     #
     # Each association is built individually so that the correct
     # Arel join node will be used for each individual association.
-    def constraints
-      @associations.each.with_index.inject([]) do |joins, (assoc, i)|
-        inject @associations[0..i], joins, assoc._join
+    def _arel
+      if @table._on
+        [@table._join.new(@table._table, @table._on)]
+      else
+        @associations.each.with_index.inject([]) do |joins, (assoc, i)|
+          inject @associations[0..i], joins, assoc._join
+        end
       end
     end
 
@@ -25,7 +32,12 @@ def inject(associations, theirs, join_node)
     end
 
     def build(names, join_node)
-      @scope.joins(names).join_sources.map do |join|
+      relation = @table._scope.joins(names)
+
+      @bind_values = relation.arel.bind_values
+      @bind_values += relation.bind_values
+
+      relation.join_sources.map do |join|
         join_node.new(join.left, join.right)
       end
     end
diff --git a/lib/baby_squeel/nodes.rb b/lib/baby_squeel/nodes.rb
index 82d9ed3..bde91b8 100644
--- a/lib/baby_squeel/nodes.rb
+++ b/lib/baby_squeel/nodes.rb
@@ -17,7 +17,7 @@ def wrap(arel)
       # ActiveRecord.
       def unwrap(node)
         if node.respond_to? :_arel
-          node._arel
+          unwrap node._arel
         elsif node.is_a? Array
           node.map { |n| unwrap(n) }
         else
@@ -94,7 +94,7 @@ def in(rel)
       end
 
       def _arel
-        parent_arel = @parent._arel
+        parent_arel = @parent._arel._arel
 
         if parent_arel && parent_arel.last
           parent_arel.last.left[@name]
diff --git a/lib/baby_squeel/table.rb b/lib/baby_squeel/table.rb
index eb88f9f..64e4c15 100644
--- a/lib/baby_squeel/table.rb
+++ b/lib/baby_squeel/table.rb
@@ -14,10 +14,10 @@ def initialize(model_name, name)
   end
 
   class Table
-    attr_accessor :_on, :_join, :_table
+    attr_accessor :_scope, :_on, :_join, :_table
 
     def initialize(scope)
-      @scope = scope
+      @_scope = scope
       @_table = scope.arel_table
       @_join = Arel::Nodes::InnerJoin
     end
@@ -30,15 +30,15 @@ def [](key)
     # Constructs a new BabySqueel::Association. Raises
     # an exception if the association is not found.
     def association(name)
-      if reflection = @scope.reflect_on_association(name)
+      if reflection = _scope.reflect_on_association(name)
         Association.new(self, reflection)
       else
-        raise AssociationNotFoundError.new(@scope.model_name, name)
+        raise AssociationNotFoundError.new(_scope.model_name, name)
       end
     end
 
     def sift(sifter_name, *args)
-      Nodes.wrap @scope.public_send("sift_#{sifter_name}", *args)
+      Nodes.wrap _scope.public_send("sift_#{sifter_name}", *args)
     end
 
     # Alias a table. This is only possible when joining
@@ -89,19 +89,15 @@ def on!(node)
     # 2. Resolve the assocition's join clauses using ActiveRecord.
     #
     def _arel(associations = [])
-      if _on
-        _join.new(_table, _on)
-      else
-        JoinDependency.new(@scope, associations).constraints
-      end
+      JoinDependency.new(self, associations)
     end
 
     private
 
     def resolve(name)
-      if @scope.column_names.include?(name.to_s)
+      if _scope.column_names.include?(name.to_s)
         self[name]
-      elsif @scope.reflect_on_association(name)
+      elsif _scope.reflect_on_association(name)
         association(name)
       end
     end
@@ -114,7 +110,7 @@ def method_missing(name, *args, &block)
       return super if !args.empty? || block_given?
 
       resolve(name) || begin
-        raise NotFoundError.new(@scope.model_name, name)
+        raise NotFoundError.new(_scope.model_name, name)
       end
     end
   end
diff --git a/spec/baby_squeel/active_record/query_methods/joining_spec.rb b/spec/baby_squeel/active_record/query_methods/joining_spec.rb
index e2c4e9b..6353696 100644
--- a/spec/baby_squeel/active_record/query_methods/joining_spec.rb
+++ b/spec/baby_squeel/active_record/query_methods/joining_spec.rb
@@ -86,6 +86,16 @@
       EOSQL
     end
 
+    it 'merges bind values' do
+      relation = Post.joining { ugly_author_comments }
+
+      expect(relation).to produce_sql(<<-EOSQL)
+        SELECT "posts".* FROM "posts"
+        INNER JOIN "authors" ON "authors"."id" = "posts"."author_id" AND "authors"."ugly" = 't'
+        INNER JOIN "comments" ON "comments"."author_id" = "authors"."id"
+      EOSQL
+    end
+
     context 'with complex conditions' do
       it 'inner joins' do
         relation = Post.joining {
diff --git a/spec/support/models.rb b/spec/support/models.rb
index 193c72b..eab31b8 100644
--- a/spec/support/models.rb
+++ b/spec/support/models.rb
@@ -3,10 +3,17 @@ class Author < ActiveRecord::Base
   has_many :comments
 end
 
+class UglyAuthor < Author
+  default_scope { where ugly: true }
+end
+
 class Post < ActiveRecord::Base
   has_many :comments
   belongs_to :author
   has_many :author_comments, through: :author, source: :comments
+
+  belongs_to :ugly_author, foreign_key: :author_id
+  has_many :ugly_author_comments, through: :ugly_author, source: :comments
 end
 
 class Comment < ActiveRecord::Base
diff --git a/spec/support/schema.rb b/spec/support/schema.rb
index ec7a411..56bdb8c 100644
--- a/spec/support/schema.rb
+++ b/spec/support/schema.rb
@@ -8,6 +8,7 @@
 ActiveRecord::Schema.define do
   create_table :authors, force: true do |t|
     t.string :name
+    t.boolean :ugly
     t.timestamps null: false
   end