diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index 0dcecbd42d422c573433be24920ca0536f542c74..55fd0e0b5238346270fa33485140bec19b92167c 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -552,8 +552,6 @@ def where(opts = :chain, *rest)
         WhereChain.new(spawn)
       elsif opts.blank?
         self
-      elsif !opts.is_a?(String) && !opts.respond_to?(:to_h)
-        raise ArgumentError, "Unsupported argument type: #{opts} (#{opts.class})"
       else
         spawn.where!(opts, *rest)
       end
diff --git a/activerecord/lib/active_record/relation/where_clause_factory.rb b/activerecord/lib/active_record/relation/where_clause_factory.rb
index 83ac074f97971dacadd9618c64f527cb85d5c20a..a81ff98e49eebf9e2e31054eb9de036e8814e5ce 100644
--- a/activerecord/lib/active_record/relation/where_clause_factory.rb
+++ b/activerecord/lib/active_record/relation/where_clause_factory.rb
@@ -20,8 +20,10 @@ def build(opts, other)
           attributes, binds = predicate_builder.create_binds(attributes)
 
           parts = predicate_builder.build_from_hash(attributes)
-        else
+        when Arel::Nodes::Node
           parts = [opts]
+        else
+          raise ArgumentError, "Unsupported argument type: #{opts} (#{opts.class})"
         end
 
         WhereClause.new(parts, binds)
diff --git a/activerecord/test/cases/relation_test.rb b/activerecord/test/cases/relation_test.rb
index b0fb905760363e6671a158d286eb7df662e13993..675149556f6cf8e3299c8ad51ac1183166e7bb80 100644
--- a/activerecord/test/cases/relation_test.rb
+++ b/activerecord/test/cases/relation_test.rb
@@ -57,9 +57,6 @@ def test_extensions
     def test_empty_where_values_hash
       relation = Relation.new(FakeKlass, :b, nil)
       assert_equal({}, relation.where_values_hash)
-
-      relation.where! :hello
-      assert_equal({}, relation.where_values_hash)
     end
 
     def test_has_values
@@ -153,10 +150,10 @@ def test_references_values_dont_duplicate
     end
 
     test 'merging a hash into a relation' do
-      relation = Relation.new(FakeKlass, :b, nil)
-      relation = relation.merge where: :lol, readonly: true
+      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
+      relation = relation.merge where: {name: :lol}, readonly: true
 
-      assert_equal Relation::WhereClause.new([:lol], []), relation.where_clause
+      assert_equal({"name"=>:lol}, relation.where_clause.to_h)
       assert_equal true, relation.readonly_value
     end
 
@@ -185,7 +182,7 @@ def test_references_values_dont_duplicate
     end
 
     test '#values returns a dup of the values' do
-      relation = Relation.new(FakeKlass, :b, nil).where! :foo
+      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder).where!(name: :foo)
       values   = relation.values
 
       values[:where] = nil