diff --git a/Framework/API/inc/MantidAPI/FileFinder.h b/Framework/API/inc/MantidAPI/FileFinder.h
index b83a60068c578b452dc6c970b91c110fd3ce8c9a..594d34c4731ea01a4b7b24eab2d32e3746ecbc7a 100644
--- a/Framework/API/inc/MantidAPI/FileFinder.h
+++ b/Framework/API/inc/MantidAPI/FileFinder.h
@@ -58,8 +58,6 @@ public:
   /// DO NOT USE! MADE PUBLIC FOR TESTING ONLY.
   std::string getExtension(const std::string &filename,
                            const std::vector<std::string> &exts) const;
-  void getUniqueExtensions(const std::vector<std::string> &exts,
-                           std::set<std::string> &uniqueExts) const;
 
 private:
   friend struct Mantid::Kernel::CreateUsingNew<FileFinderImpl>;
@@ -79,6 +77,8 @@ private:
                              const std::set<std::string> &filenames,
                              const std::vector<std::string> &exts) const;
   std::string toUpper(const std::string &src) const;
+  void getUniqueExtensions(const std::vector<std::string> &exts,
+                           std::set<std::string> &uniqueExts) const;
   /// glob option - set to case sensitive or insensitive
   int m_globOption;
 };
diff --git a/Framework/API/src/FileFinder.cpp b/Framework/API/src/FileFinder.cpp
index aa035053c493bd8d2fca5a1e2b23afb4b4920325..4282d96b536f9c60c176409da865ca584d78b274 100644
--- a/Framework/API/src/FileFinder.cpp
+++ b/Framework/API/src/FileFinder.cpp
@@ -512,6 +512,14 @@ FileFinderImpl::findRun(const std::string &hintstr,
   return "";
 }
 
+/**
+ * Given a set of already determined extensions and new extensions,
+ * create a set of all extensions.
+ * If not in an extension-is-case-sensitive environment, only add the
+ * lower case OR upper case version of the extension
+ * @param exts :: a vector of extensions to add
+ * @param uniqueExts :: a set of currently included extensions
+ */
 void FileFinderImpl::getUniqueExtensions(
     const std::vector<std::string> &exts,
     std::set<std::string> &uniqueExts) const {
diff --git a/Framework/API/test/FileFinderTest.h b/Framework/API/test/FileFinderTest.h
index 60255b78e7cd760d7e5d81ade178f897b495a5ac..3c9d1979283a6f976e4a67eeee4deb17fc4ce088 100644
--- a/Framework/API/test/FileFinderTest.h
+++ b/Framework/API/test/FileFinderTest.h
@@ -347,22 +347,6 @@ public:
     std::cout << "\n end of test \n";
   }
 
-  void testGetUniqueExtensions() {
-    std::set<std::string> uniqueExts;
-    std::vector<std::string> firstExtsToAdd = {".RAW", ".log"};
-    std::vector<std::string> secondExtsToAdd = {".so", ".txt", ".RAW"};
-
-    std::set<std::string> expectedFirstExtensions = {".RAW", ".log"};
-    std::set<std::string> expectedSecondExtensions = {".RAW", ".log", ".so",
-                                                      ".txt"};
-
-    FileFinder::Instance().getUniqueExtensions(firstExtsToAdd, uniqueExts);
-    TS_ASSERT_EQUALS(uniqueExts, expectedFirstExtensions);
-
-    FileFinder::Instance().getUniqueExtensions(secondExtsToAdd, uniqueExts);
-    TS_ASSERT_EQUALS(uniqueExts, expectedSecondExtensions);
-  }
-
   void testFindAddFiles() {
     // create a test file to find
     Poco::File file("LOQ00111-add.raw");