diff --git a/lib/detectify/query_builder/base.rb b/lib/detectify/query_builder/base.rb
index 466042f..6563ff4 100644
--- a/lib/detectify/query_builder/base.rb
+++ b/lib/detectify/query_builder/base.rb
@@ -4,8 +4,8 @@ class Base
       attr_reader :domain, :subdomain
 
       def initialize(domain, subdomain)
-        @domain    = domain
-        @subdomain = subdomain
+        @domain    = domain.downcase if domain.is_a?(String)
+        @subdomain = subdomain.downcase if subdomain.is_a?(String)
       end
 
       def build
diff --git a/lib/detectify/query_builder/sql.rb b/lib/detectify/query_builder/sql.rb
index 92513f4..05441d5 100644
--- a/lib/detectify/query_builder/sql.rb
+++ b/lib/detectify/query_builder/sql.rb
@@ -13,11 +13,11 @@ def build
       private
 
       def domain_clause
-        "#{Detectify.config.domain_column} = ?" if need_domain_clause?
+        "LOWER(#{Detectify.config.domain_column}) = ?" if need_domain_clause?
       end
 
       def subdomain_clause
-        "#{Detectify.config.subdomain_column} = ?" if need_subdomain_clause?
+        "LOWER(#{Detectify.config.subdomain_column}) = ?" if need_subdomain_clause?
       end
 
       def or_operator
diff --git a/spec/detectify/query_builder/base_spec.rb b/spec/detectify/query_builder/base_spec.rb
new file mode 100644
index 0000000..de2755f
--- /dev/null
+++ b/spec/detectify/query_builder/base_spec.rb
@@ -0,0 +1,17 @@
+require 'spec_helper'
+
+RSpec.describe Detectify::QueryBuilder::Base do
+  let(:domain) { 'DOMAIN' }
+  let(:subdomain) { 'SUBDOMAIN' }
+  subject { Detectify::QueryBuilder::Base.new(domain, subdomain) }
+
+  describe '#initialize' do
+    it 'sets domain in downcase' do
+      expect(subject.domain).to eq(domain.downcase)
+    end
+
+    it 'sets subdomain in downcase' do
+      expect(subject.subdomain).to eq(subdomain.downcase)
+    end
+  end
+end
diff --git a/spec/detectify/query_builder/sql_spec.rb b/spec/detectify/query_builder/sql_spec.rb
index c469698..6795e17 100644
--- a/spec/detectify/query_builder/sql_spec.rb
+++ b/spec/detectify/query_builder/sql_spec.rb
@@ -9,14 +9,14 @@
         let(:domain) { 'example.com' }
         let(:subdomain) { nil }
 
-        it { is_expected.to eq(['domain = ?', 'example.com']) }
+        it { is_expected.to eq(['LOWER(domain) = ?', 'example.com']) }
       end
 
       context 'with only subdomain' do
         let(:domain) { nil }
         let(:subdomain) { 'example' }
 
-        it { is_expected.to eq(['subdomain = ?', 'example']) }
+        it { is_expected.to eq(['LOWER(subdomain) = ?', 'example']) }
       end
 
       context 'with domain and subdomain' do
@@ -25,7 +25,7 @@
 
         it do
           is_expected.to eq([
-            'domain = ? OR subdomain = ?', 'example.com', 'example'
+            'LOWER(domain) = ? OR LOWER(subdomain) = ?', 'example.com', 'example'
           ])
         end
       end
@@ -38,7 +38,7 @@
         let(:domain) { 'example.com' }
         let(:subdomain) { nil }
 
-        it { is_expected.to eq(['domain = ?', 'example.com']) }
+        it { is_expected.to eq(['LOWER(domain) = ?', 'example.com']) }
       end
 
       context 'with only subdomain' do
@@ -52,7 +52,7 @@
         let(:domain) { 'example.com' }
         let(:subdomain) { 'example' }
 
-        it { is_expected.to eq(['domain = ?', 'example.com']) }
+        it { is_expected.to eq(['LOWER(domain) = ?', 'example.com']) }
       end
 
       after { Detectify.reset_config }
@@ -72,14 +72,14 @@
         let(:domain) { nil }
         let(:subdomain) { 'example' }
 
-        it { is_expected.to eq(['subdomain = ?', 'example']) }
+        it { is_expected.to eq(['LOWER(subdomain) = ?', 'example']) }
       end
 
       context 'with domain and subdomain' do
         let(:domain) { 'example.com' }
         let(:subdomain) { 'example' }
 
-        it { is_expected.to eq(['subdomain = ?', 'example']) }
+        it { is_expected.to eq(['LOWER(subdomain) = ?', 'example']) }
       end
 
       after { Detectify.reset_config }