diff --git a/app/models/ci/group_variable.rb b/app/models/ci/group_variable.rb
index afeae69ba39..1dd0e050ba9 100644
--- a/app/models/ci/group_variable.rb
+++ b/app/models/ci/group_variable.rb
@@ -6,7 +6,10 @@ module Ci
 
     belongs_to :group
 
-    validates :key, uniqueness: { scope: :group_id }
+    validates :key, uniqueness: {
+      scope: :group_id,
+      message: "(%{value}) has already been taken"
+    }
 
     scope :unprotected, -> { where(protected: false) }
   end
diff --git a/app/models/ci/variable.rb b/app/models/ci/variable.rb
index 67d3ec81b6f..7c71291de84 100644
--- a/app/models/ci/variable.rb
+++ b/app/models/ci/variable.rb
@@ -6,7 +6,10 @@ module Ci
 
     belongs_to :project
 
-    validates :key, uniqueness: { scope: [:project_id, :environment_scope] }
+    validates :key, uniqueness: {
+      scope: [:project_id, :environment_scope],
+      message: "(%{value}) has already been taken"
+    }
 
     scope :unprotected, -> { where(protected: false) }
   end
diff --git a/spec/models/ci/group_variable_spec.rb b/spec/models/ci/group_variable_spec.rb
index 145189e7469..1b10501701c 100644
--- a/spec/models/ci/group_variable_spec.rb
+++ b/spec/models/ci/group_variable_spec.rb
@@ -5,7 +5,7 @@ describe Ci::GroupVariable do
 
   it { is_expected.to include_module(HasVariable) }
   it { is_expected.to include_module(Presentable) }
-  it { is_expected.to validate_uniqueness_of(:key).scoped_to(:group_id) }
+  it { is_expected.to validate_uniqueness_of(:key).scoped_to(:group_id).with_message(/\(\w+\) has already been taken/) }
 
   describe '.unprotected' do
     subject { described_class.unprotected }
diff --git a/spec/models/ci/variable_spec.rb b/spec/models/ci/variable_spec.rb
index e4ff551151e..875e8b2b682 100644
--- a/spec/models/ci/variable_spec.rb
+++ b/spec/models/ci/variable_spec.rb
@@ -6,7 +6,7 @@ describe Ci::Variable do
   describe 'validations' do
     it { is_expected.to include_module(HasVariable) }
     it { is_expected.to include_module(Presentable) }
-    it { is_expected.to validate_uniqueness_of(:key).scoped_to(:project_id, :environment_scope) }
+    it { is_expected.to validate_uniqueness_of(:key).scoped_to(:project_id, :environment_scope).with_message(/\(\w+\) has already been taken/) }
   end
 
   describe '.unprotected' do