diff --git a/src/server/kiwix-serve.cpp b/src/server/kiwix-serve.cpp
index 395af3f..5f9f79c 100644
--- a/src/server/kiwix-serve.cpp
+++ b/src/server/kiwix-serve.cpp
@@ -79,6 +79,7 @@ using namespace std;
 static bool nosearchbarFlag = false;
 static string welcomeHTML;
 static bool verboseFlag = false;
+static std::map<std::string, std::string> extMimeTypes;
 static std::map<std::string, kiwix::Reader*> readers;
 static std::map<std::string, kiwix::Searcher*> searchers;
 static pthread_mutex_t readerLock = PTHREAD_MUTEX_INITIALIZER;
@@ -88,58 +89,25 @@ static pthread_mutex_t searcherLock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_mutex_t compressorLock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_mutex_t resourceLock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_mutex_t verboseFlagLock = PTHREAD_MUTEX_INITIALIZER;
+static pthread_mutex_t mimeTypeLock = PTHREAD_MUTEX_INITIALIZER;
 
 /* Try to get the mimeType from the file extension */
 static std::string getMimeTypeForFile(const std::string& filename) {
-
-  std::map<std::string, std::string> extMimeTypes;
-  extMimeTypes["HTML"] = "text/html";
-  extMimeTypes["html"] = "text/html";
-  extMimeTypes["HTM"] = "text/html";
-  extMimeTypes["htm"] = "text/html";
-  extMimeTypes["PNG"] = "image/png";
-  extMimeTypes["png"] = "image/png";
-  extMimeTypes["TIFF"] = "image/tiff";
-  extMimeTypes["tiff"] = "image/tiff";
-  extMimeTypes["TIF"] = "image/tiff";
-  extMimeTypes["tif"] = "image/tiff";
-  extMimeTypes["JPEG"] = "image/jpeg";
-  extMimeTypes["jpeg"] = "image/jpeg";
-  extMimeTypes["JPG"] = "image/jpeg";
-  extMimeTypes["jpg"] = "image/jpeg";
-  extMimeTypes["GIF"] = "image/gif";
-  extMimeTypes["gif"] = "image/gif";
-  extMimeTypes["SVG"] = "image/svg+xml";
-  extMimeTypes["svg"] = "image/svg+xml";
-  extMimeTypes["TXT"] = "text/plain";
-  extMimeTypes["txt"] = "text/plain";
-  extMimeTypes["XML"] = "text/xml";
-  extMimeTypes["xml"] = "text/xml";
-  extMimeTypes["PDF"] = "application/pdf";
-  extMimeTypes["pdf"] = "application/pdf";
-  extMimeTypes["OGG"] = "application/ogg";
-  extMimeTypes["ogg"] = "application/ogg";
-  extMimeTypes["JS"] = "application/javascript";
-  extMimeTypes["js"] = "application/javascript";
-  extMimeTypes["CSS"] = "text/css";
-  extMimeTypes["css"] = "text/css";
-  extMimeTypes["otf"] = "application/vnd.ms-opentype";
-  extMimeTypes["OTF"] = "application/vnd.ms-opentype";
-  extMimeTypes["ttf"] = "application/font-ttf";
-  extMimeTypes["TTF"] = "application/font-ttf";
-  extMimeTypes["woff"] = "application/font-woff";
-  extMimeTypes["WOFF"] = "application/font-woff";
-  extMimeTypes["vtt"] = "text/vtt";
-  extMimeTypes["VTT"] = "text/vtt";
+  std::string mimeType = "text/plain";
 
   if (filename.find_last_of(".") != std::string::npos) {
     std::string mimeType = filename.substr(filename.find_last_of(".")+1);
-    if (extMimeTypes.find(mimeType) != extMimeTypes.end()) {
-      return extMimeTypes[mimeType];
+
+    pthread_mutex_lock(&mimeTypeLock);
+    if (extMimeTypes.find(mimeType) != extMimeTypes.end() ||
+	extMimeTypes.find(kiwix::ucAll(mimeType)) != extMimeTypes.end()	
+	) {
+      mimeType = extMimeTypes[mimeType];
     }
+    pthread_mutex_unlock(&mimeTypeLock);
   }
 
-  return "text/plain";
+  return mimeType;
 }
 
 void introduceTaskbar(string &content, const string &humanReadableBookId) {
@@ -693,7 +661,29 @@ int main(int argc, char **argv) {
   pthread_mutex_init(&compressorLock, NULL);
   pthread_mutex_init(&resourceLock, NULL);
   pthread_mutex_init(&verboseFlagLock, NULL);
-
+  pthread_mutex_init(&mimeTypeLock, NULL);
+  
+  /* Hard coded mimetypes */
+  extMimeTypes["html"] = "text/html";
+  extMimeTypes["htm"] = "text/html";
+  extMimeTypes["png"] = "image/png";
+  extMimeTypes["tiff"] = "image/tiff";
+  extMimeTypes["tif"] = "image/tiff";
+  extMimeTypes["jpeg"] = "image/jpeg";
+  extMimeTypes["jpg"] = "image/jpeg";
+  extMimeTypes["gif"] = "image/gif";
+  extMimeTypes["svg"] = "image/svg+xml";
+  extMimeTypes["txt"] = "text/plain";
+  extMimeTypes["xml"] = "text/xml";
+  extMimeTypes["pdf"] = "application/pdf";
+  extMimeTypes["ogg"] = "application/ogg";
+  extMimeTypes["js"] = "application/javascript";
+  extMimeTypes["css"] = "text/css";
+  extMimeTypes["otf"] = "application/vnd.ms-opentype";
+  extMimeTypes["ttf"] = "application/font-ttf";
+  extMimeTypes["woff"] = "application/font-woff";
+  extMimeTypes["vtt"] = "text/vtt";
+  
   /* Start the HTTP daemon */
   void *page = NULL;
   daemon = MHD_start_daemon(MHD_USE_SELECT_INTERNALLY,
@@ -753,5 +743,6 @@ int main(int argc, char **argv) {
   pthread_mutex_destroy(&mapLock);
   pthread_mutex_destroy(&welcomeLock);
   pthread_mutex_destroy(&verboseFlagLock);
+  pthread_mutex_destroy(&mimeTypeLock);
   exit(0);
 }