diff --git a/lib/simplecov.rb b/lib/simplecov.rb
index da88b055..19665f7c 100644
--- a/lib/simplecov.rb
+++ b/lib/simplecov.rb
@@ -57,9 +57,9 @@ def start(profile = nil, &block)
     # their coverage to zero.
     #
     def add_not_loaded_files(result)
-      if track_files
+      if tracked_files
         result = result.dup
-        Dir[track_files].each do |file|
+        Dir[tracked_files].each do |file|
           absolute = File.expand_path(file)
 
           result[absolute] ||= [0] * File.foreach(absolute).count
diff --git a/lib/simplecov/configuration.rb b/lib/simplecov/configuration.rb
index dec0ca26..23ddc143 100644
--- a/lib/simplecov/configuration.rb
+++ b/lib/simplecov/configuration.rb
@@ -50,11 +50,18 @@ def coverage_path
     # or not they were explicitly required. Without this, un-required files
     # will not be present in the final report.
     #
-    def track_files(glob = nil)
-      return @track_files if defined?(@track_files) && glob.nil?
+    def track_files(glob)
       @track_files = glob
     end
 
+    #
+    # Returns the glob that will be used to include files that were not
+    # explicitly required.
+    #
+    def tracked_files
+      @track_files if defined?(@track_files)
+    end
+
     #
     # Returns the list of configured filters. Add filters using SimpleCov.add_filter.
     #
diff --git a/spec/configuration_spec.rb b/spec/configuration_spec.rb
new file mode 100644
index 00000000..2c88f7a4
--- /dev/null
+++ b/spec/configuration_spec.rb
@@ -0,0 +1,29 @@
+require "helper"
+
+describe SimpleCov::Configuration do
+  describe "#tracked_files" do
+    context "when configured" do
+      let(:glob) { "{app,lib}/**/*.rb" }
+
+      before { SimpleCov.track_files(glob) }
+
+      it "returns the configured glob" do
+        expect(SimpleCov.tracked_files).to eq glob
+      end
+
+      context "and configured again with nil" do
+        before { SimpleCov.track_files(nil) }
+
+        it "returns nil" do
+          expect(SimpleCov.tracked_files).to be_nil
+        end
+      end
+    end
+
+    context "when unconfigured" do
+      it "returns nil" do
+        expect(SimpleCov.tracked_files).to be_nil
+      end
+    end
+  end
+end