diff --git a/tests/samples/codefiles/fsharp.fs b/tests/samples/codefiles/fsharp.fs
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_languages.py b/tests/test_languages.py
index ceba91b..0af44c6 100644
--- a/tests/test_languages.py
+++ b/tests/test_languages.py
@@ -221,3 +221,19 @@ class LanguagesTestCase(utils.TestCase):
 
         language = u('Perl')
         self.assertEqual(self.patched['wakatime.offlinequeue.Queue.push'].call_args[0][0].get('language'), language)
+
+    def test_fsharp_detected_over_forth(self):
+        response = Response()
+        response.status_code = 500
+        self.patched['wakatime.packages.requests.adapters.HTTPAdapter.send'].return_value = response
+
+        now = u(int(time.time()))
+        config = 'tests/samples/configs/good_config.cfg'
+        entity = 'tests/samples/codefiles/fsharp.fs'
+        args = ['--file', entity, '--config', config, '--time', now]
+
+        retval = execute(args)
+        self.assertEquals(retval, 102)
+
+        language = u('F#')
+        self.assertEqual(self.patched['wakatime.offlinequeue.Queue.push'].call_args[0][0].get('language'), language)
diff --git a/wakatime/packages/pygments/lexers/_mapping.py b/wakatime/packages/pygments/lexers/_mapping.py
index b48ee1d..57112f4 100644
--- a/wakatime/packages/pygments/lexers/_mapping.py
+++ b/wakatime/packages/pygments/lexers/_mapping.py
@@ -148,7 +148,7 @@ LEXERS = {
     'EvoqueLexer': ('pygments.lexers.templates', 'Evoque', ('evoque',), ('*.evoque',), ('application/x-evoque',)),
     'EvoqueXmlLexer': ('pygments.lexers.templates', 'XML+Evoque', ('xml+evoque',), ('*.xml',), ('application/xml+evoque',)),
     'EzhilLexer': ('pygments.lexers.ezhil', 'Ezhil', ('ezhil',), ('*.n',), ('text/x-ezhil',)),
-    'FSharpLexer': ('pygments.lexers.dotnet', 'FSharp', ('fsharp',), ('*.fs', '*.fsi'), ('text/x-fsharp',)),
+    'FSharpLexer': ('pygments.lexers.dotnet', 'F#', ('fsharp',), ('*.fs', '*.fsi'), ('text/x-fsharp',)),
     'FactorLexer': ('pygments.lexers.factor', 'Factor', ('factor',), ('*.factor',), ('text/x-factor',)),
     'FancyLexer': ('pygments.lexers.ruby', 'Fancy', ('fancy', 'fy'), ('*.fy', '*.fancypack'), ('text/x-fancysrc',)),
     'FantomLexer': ('pygments.lexers.fantom', 'Fantom', ('fan',), ('*.fan',), ('application/x-fantom',)),
diff --git a/wakatime/packages/pygments/lexers/dotnet.py b/wakatime/packages/pygments/lexers/dotnet.py
index 4e2bc8a..a60c579 100644
--- a/wakatime/packages/pygments/lexers/dotnet.py
+++ b/wakatime/packages/pygments/lexers/dotnet.py
@@ -549,7 +549,7 @@ class FSharpLexer(RegexLexer):
     .. versionadded:: 1.5
     """
 
-    name = 'FSharp'
+    name = 'F#'
     aliases = ['fsharp']
     filenames = ['*.fs', '*.fsi']
     mimetypes = ['text/x-fsharp']
diff --git a/wakatime/stats.py b/wakatime/stats.py
index 50392aa..f91ce01 100644
--- a/wakatime/stats.py
+++ b/wakatime/stats.py
@@ -311,6 +311,7 @@ def custom_pygments_guess_lexer_for_filename(_fn, _text, **options):
 def customize_priority(lexer):
     """Return an integer priority for the given lexer object."""
 
-    if lexer.name.lower() in LANGUAGES:
-        lexer.priority = LANGUAGES[lexer.name.lower()]
+    lexer_name = lexer.name.lower().replace('sharp', '#')
+    if lexer_name in LANGUAGES:
+        lexer.priority = LANGUAGES[lexer_name]
     return lexer