diff --git a/config/flay.yml b/config/flay.yml
index 3b125cc5..3c2258be 100644
--- a/config/flay.yml
+++ b/config/flay.yml
@@ -1,3 +1,3 @@
 ---
 threshold: 18
-total_score: 1204
+total_score: 1208
diff --git a/config/reek.yml b/config/reek.yml
index 00f151f7..76628b8a 100644
--- a/config/reek.yml
+++ b/config/reek.yml
@@ -130,6 +130,7 @@ UtilityFunction:
   - Mutant::Integration::Null#call
   - Mutant::Integration::Rspec#parse_example
   - Mutant::Meta::Example::Verification#format_mutation
+  - Mutant::Repository::Diff#tracks? # intentional, private
   - Mutant::Reporter::CLI::Format::Progressive#new_buffer
   - Mutant::Reporter::CLI::Printer::StatusProgressive#object # False positive calls super
   - Mutant::Integration::Rspec#parse_expression # intentional, private
diff --git a/lib/mutant/repository.rb b/lib/mutant/repository.rb
index 97b2af31..6b230e68 100644
--- a/lib/mutant/repository.rb
+++ b/lib/mutant/repository.rb
@@ -48,6 +48,8 @@ module Mutant
       #
       # @api private
       def touches?(path, line_range)
+        return false unless tracks?(path)
+
         command = %W[
           git log
           #{from}...#{to}
@@ -61,6 +63,26 @@ module Mutant
         !stdout.empty?
       end
 
+    private
+
+      # Test if path is tracked in repository
+      #
+      # FIXME: Cache results, to avoid spending time on producing redundant results.
+      #
+      # @param [Pathname] path
+      #
+      # @return [Boolean]
+      #
+      # @api private
+      def tracks?(path)
+        command = %W[git ls-files --error-unmatch -- #{path}]
+        Kernel.system(
+          *command,
+          out: File::NULL,
+          err: File::NULL
+        )
+      end
+
     end # Diff
   end # Repository
 end # Mutant
diff --git a/spec/unit/mutant/repository/diff_spec.rb b/spec/unit/mutant/repository/diff_spec.rb
index 4ff24109..92b53d40 100644
--- a/spec/unit/mutant/repository/diff_spec.rb
+++ b/spec/unit/mutant/repository/diff_spec.rb
@@ -11,49 +11,69 @@ describe Mutant::Repository::Diff do
     let(:object)        { described_class.new('from_rev', 'to_rev') }
     let(:path)          { Pathname.new('foo.rb')                    }
     let(:line_range)    { 1..2                                      }
-    let(:status)        { double('Status', success?: success?)      }
-    let(:stdout)        { double('Stdout', empty?: stdout_empty?)   }
-    let(:stdout_empty?) { false                                     }
 
     subject { object.touches?(path, line_range) }
 
     before do
-      expect(Open3).to receive(:capture2)
+      expect(Kernel).to receive(:system)
         .ordered
-        .with(*expected_git_log_command, binmode: true)
-        .and_return([stdout, status])
+        .with(
+          *%w[git ls-files --error-unmatch -- foo.rb],
+          out: File::NULL,
+          err: File::NULL
+        ).and_return(git_ls_success?)
     end
 
-    let(:expected_git_log_command) do
-      %w[
-        git log from_rev...to_rev -L 1,2:foo.rb
-      ]
+    context 'when file is NOT tracked in repository' do
+      let(:git_ls_success?) { false }
+
+      it { should be(false) }
     end
 
-    context 'on failure of git log command' do
-      let(:success?) { false }
+    context 'when file is tracked in repository' do
+      let(:git_ls_success?) { true                                    }
+      let(:status)          { double('Status', success?: success?)    }
+      let(:stdout)          { double('Stdout', empty?: stdout_empty?) }
+      let(:stdout_empty?)   { false                                   }
 
-      it 'raises error' do
-        expect { subject }.to raise_error(
-          Mutant::Repository::RepositoryError,
-          "Command #{expected_git_log_command} failed!"
-        )
-      end
-    end
-
-    context 'on suuccess of git command' do
-      let(:success?) { true }
-
-      context 'on empty stdout' do
-        let(:stdout_empty?) { true }
-
-        it { should be(false) }
+      before do
+        expect(Open3).to receive(:capture2)
+          .ordered
+          .with(*expected_git_log_command, binmode: true)
+          .and_return([stdout, status])
       end
 
-      context 'on non empty stdout' do
-        let(:stdout_empty?) { false }
+      let(:expected_git_log_command) do
+        %w[
+          git log from_rev...to_rev -L 1,2:foo.rb
+        ]
+      end
 
-        it { should be(true) }
+      context 'on failure of git log command' do
+        let(:success?) { false }
+
+        it 'raises error' do
+          expect { subject }.to raise_error(
+            Mutant::Repository::RepositoryError,
+            "Command #{expected_git_log_command} failed!"
+          )
+        end
+      end
+
+      context 'on suuccess of git command' do
+        let(:success?) { true }
+
+        context 'on empty stdout' do
+          let(:stdout_empty?) { true }
+
+          it { should be(false) }
+        end
+
+        context 'on non empty stdout' do
+          let(:stdout_empty?) { false }
+
+          it { should be(true) }
+        end
       end
     end
   end