diff --git a/src/config.cc b/src/config.cc
index 2941f38..74c2a67 100644
--- a/src/config.cc
+++ b/src/config.cc
@@ -28,7 +28,7 @@ Config::Config() {
   
 #ifdef _WIN32
      auto env_MSYSTEM_PREFIX=std::getenv("MSYSTEM_PREFIX");
-     if(env_MSYSTEM_PREFIX!=NULL)
+     if(env_MSYSTEM_PREFIX!=nullptr)
        terminal.msys2_mingw_path=boost::filesystem::path(env_MSYSTEM_PREFIX);
 #endif
 }
diff --git a/src/debug_lldb.cc b/src/debug_lldb.cc
index 57d269e..36f683e 100644
--- a/src/debug_lldb.cc
+++ b/src/debug_lldb.cc
@@ -80,7 +80,7 @@ void Debug::LLDB::start(const std::string &command, const boost::filesystem::pat
   const char *argv[arguments.size()+1];
   for(size_t c=0;c<arguments.size();c++)
     argv[c]=arguments[c].c_str();
-  argv[arguments.size()]=NULL;
+  argv[arguments.size()]=nullptr;
   
   auto target=debugger->CreateTarget(executable.c_str());
   if(!target.IsValid()) {
@@ -310,11 +310,11 @@ std::vector<Debug::LLDB::Frame> Debug::LLDB::get_backtrace() {
       
       backtrace_frame.index=c_f;
       
-      if(frame.GetFunctionName()!=NULL)
+      if(frame.GetFunctionName()!=nullptr)
         backtrace_frame.function_name=frame.GetFunctionName();
       
       auto module_filename=frame.GetModule().GetFileSpec().GetFilename();
-      if(module_filename!=NULL) {
+      if(module_filename!=nullptr) {
         backtrace_frame.module_filename=module_filename;
       }
       
@@ -351,7 +351,7 @@ std::vector<Debug::LLDB::Variable> Debug::LLDB::get_variables() {
           Debug::LLDB::Variable variable;
           variable.thread_index_id=thread.GetIndexID();
           variable.frame_index=c_f;
-          if(value.GetName()!=NULL)
+          if(value.GetName()!=nullptr)
             variable.name=value.GetName();
           value.GetDescription(stream);
           variable.value=stream.GetData();
@@ -417,7 +417,7 @@ std::string Debug::LLDB::get_value(const std::string &variable, const boost::fil
       lldb::SBStream stream;
       auto value=values.GetValueAtIndex(value_index);
 
-      if(value.GetName()!=NULL && value.GetName()==variable) {
+      if(value.GetName()!=nullptr && value.GetName()==variable) {
         auto declaration=value.GetDeclaration();
         if(declaration.IsValid()) {
           if(declaration.GetLine()==line_nr && (declaration.GetColumn()==0 || declaration.GetColumn()==line_index)) {
diff --git a/src/dialogs.cc b/src/dialogs.cc
index 39122b6..1baba08 100644
--- a/src/dialogs.cc
+++ b/src/dialogs.cc
@@ -24,8 +24,8 @@ Dialog::Message::Message(const std::string &text): Gtk::MessageDialog(text, fals
   
   show_now();
   
-  while(g_main_context_pending(NULL))
-    g_main_context_iteration(NULL, false);
+  while(g_main_context_pending(nullptr))
+    g_main_context_iteration(nullptr, false);
 }
 
 bool Dialog::Message::on_delete_event(GdkEventAny *event) {
diff --git a/src/git.cc b/src/git.cc
index a996a8c..6d0666e 100644
--- a/src/git.cc
+++ b/src/git.cc
@@ -8,7 +8,7 @@ std::mutex Git::repositories_mutex;
 
 std::string Git::Error::message() noexcept {
   const git_error *last_error = giterr_last();
-  if(last_error==NULL)
+  if(last_error==nullptr)
     return std::string();
   else
     return last_error->message;
@@ -49,9 +49,9 @@ Git::Repository::Diff::Lines Git::Repository::Diff::get_lines(const std::string
   Error error;
   std::lock_guard<std::mutex> lock(mutex);
 #if LIBGIT2_SOVERSION>=23
-  error.code=git_diff_blob_to_buffer(blob.get(), NULL, buffer.c_str(), buffer.size(), NULL, &options, NULL, NULL, hunk_cb, NULL, &lines);
+  error.code=git_diff_blob_to_buffer(blob.get(), nullptr, buffer.c_str(), buffer.size(), nullptr, &options, nullptr, nullptr, hunk_cb, nullptr, &lines);
 #else
-  error.code=git_diff_blob_to_buffer(blob.get(), NULL, buffer.c_str(), buffer.size(), NULL, &options, NULL, hunk_cb, NULL, &lines);
+  error.code=git_diff_blob_to_buffer(blob.get(), nullptr, buffer.c_str(), buffer.size(), nullptr, &options, nullptr, hunk_cb, nullptr, &lines);
 #endif
   if(error)
     throw std::runtime_error(error.message());
@@ -77,9 +77,9 @@ std::string Git::Repository::Diff::get_details(const std::string &buffer, int li
   Error error;
   std::lock_guard<std::mutex> lock(mutex);
 #if LIBGIT2_SOVERSION>=23
-  error.code=git_diff_blob_to_buffer(blob.get(), NULL, buffer.c_str(), buffer.size(), NULL, &options, NULL, NULL, NULL, line_cb, &details);
+  error.code=git_diff_blob_to_buffer(blob.get(), nullptr, buffer.c_str(), buffer.size(), nullptr, &options, nullptr, nullptr, nullptr, line_cb, &details);
 #else
-  error.code=git_diff_blob_to_buffer(blob.get(), NULL, buffer.c_str(), buffer.size(), NULL, &options, NULL, NULL, line_cb, &details);
+  error.code=git_diff_blob_to_buffer(blob.get(), nullptr, buffer.c_str(), buffer.size(), nullptr, &options, nullptr, nullptr, line_cb, &details);
 #endif
   if(error)
     throw std::runtime_error(error.message());
@@ -92,7 +92,7 @@ Git::Repository::Repository(const boost::filesystem::path &path) {
     Error error;
     std::lock_guard<std::mutex> lock(mutex);
     auto path_str=path.generic_string();
-    error.code = git_repository_open_ext(&repository_ptr, path_str.c_str(), 0, NULL);
+    error.code = git_repository_open_ext(&repository_ptr, path_str.c_str(), 0, nullptr);
     if(error)
       throw std::runtime_error(error.message());
   }
@@ -235,7 +235,7 @@ boost::filesystem::path Git::Repository::get_root_path(const boost::filesystem::
     Error error;
     std::lock_guard<std::mutex> lock(mutex);
     auto path_str=path.generic_string();
-    error.code = git_repository_discover(&root, path_str.c_str(), 0, NULL);
+    error.code = git_repository_discover(&root, path_str.c_str(), 0, nullptr);
     if(error)
       throw std::runtime_error(error.message());
   }
diff --git a/src/notebook.cc b/src/notebook.cc
index 7ce9208..912eae3 100644
--- a/src/notebook.cc
+++ b/src/notebook.cc
@@ -159,8 +159,8 @@ void Notebook::open(const boost::filesystem::path &file_path, size_t notebook_in
     source_views.emplace_back(new Source::GenericView(file_path, language));
   
   source_views.back()->scroll_to_cursor_delayed=[this](Source::View* view, bool center, bool show_tooltips) {
-    while(g_main_context_pending(NULL))
-      g_main_context_iteration(NULL, false);
+    while(g_main_context_pending(nullptr))
+      g_main_context_iteration(nullptr, false);
     if(get_current_view()==view) {
       if(center)
         view->scroll_to(view->get_buffer()->get_insert(), 0.0, 1.0, 0.5);
diff --git a/src/project.cc b/src/project.cc
index b3b6a99..4decbd7 100644
--- a/src/project.cc
+++ b/src/project.cc
@@ -592,8 +592,8 @@ void Project::Markdown::compile_and_run() {
 #ifdef __linux
         uri="file://"+uri;
 #endif
-        GError* error=NULL;
-        gtk_show_uri(NULL, uri.c_str(), GDK_CURRENT_TIME, &error);
+        GError* error=nullptr;
+        gtk_show_uri(nullptr, uri.c_str(), GDK_CURRENT_TIME, &error);
         g_clear_error(&error);
 #endif
       }
@@ -625,8 +625,8 @@ void Project::HTML::compile_and_run() {
 #ifdef __linux
   uri="file://"+uri;
 #endif
-  GError* error=NULL;
-  gtk_show_uri(NULL, uri.c_str(), GDK_CURRENT_TIME, &error);
+  GError* error=nullptr;
+  gtk_show_uri(nullptr, uri.c_str(), GDK_CURRENT_TIME, &error);
   g_clear_error(&error);
 #endif
 }
diff --git a/src/selectiondialog.cc b/src/selectiondialog.cc
index 5bfd1f2..a4d6735 100644
--- a/src/selectiondialog.cc
+++ b/src/selectiondialog.cc
@@ -122,8 +122,8 @@ void SelectionDialogBase::show() {
       cursor_changed();
     }
     else if(list_view_text.get_model()->children().begin()!=list_view_text.get_selection()->get_selected()) {
-      while(g_main_context_pending(NULL))
-        g_main_context_iteration(NULL, false);
+      while(g_main_context_pending(nullptr))
+        g_main_context_iteration(nullptr, false);
       list_view_text.scroll_to_row(list_view_text.get_model()->get_path(list_view_text.get_selection()->get_selected()), 0.5);
     }
   }
diff --git a/src/source.cc b/src/source.cc
index 68d431e..e10a105 100644
--- a/src/source.cc
+++ b/src/source.cc
@@ -30,7 +30,7 @@ namespace sigc {
 Glib::RefPtr<Gsv::Language> Source::guess_language(const boost::filesystem::path &file_path) {
   auto language_manager=Gsv::LanguageManager::get_default();
   bool result_uncertain = false;
-  auto content_type = Gio::content_type_guess(file_path.string(), NULL, 0, result_uncertain);
+  auto content_type = Gio::content_type_guess(file_path.string(), nullptr, 0, result_uncertain);
   if(result_uncertain) {
     content_type.clear();
   }
@@ -380,7 +380,7 @@ void Source::View::configure() {
     diagnostic_tag_underline->property_underline()=Pango::Underline::UNDERLINE_ERROR;
     auto tag_class=G_OBJECT_GET_CLASS(diagnostic_tag_underline->gobj()); //For older GTK+ 3 versions:
     auto param_spec=g_object_class_find_property(tag_class, "underline-rgba");
-    if(param_spec!=NULL) {
+    if(param_spec!=nullptr) {
       diagnostic_tag_underline->set_property("underline-rgba", Gdk::RGBA(warning_property));
     }
   }
@@ -509,7 +509,7 @@ void Source::View::search_highlight(const std::string &text, bool case_sensitive
   gtk_source_search_settings_set_case_sensitive(search_settings, case_sensitive);
   gtk_source_search_settings_set_regex_enabled(search_settings, regex);
   gtk_source_search_settings_set_search_text(search_settings, text.c_str());
-  search_occurrences_updated(NULL, NULL, this);
+  search_occurrences_updated(nullptr, nullptr, this);
 }
 
 void Source::View::search_forward() {
@@ -541,7 +541,7 @@ void Source::View::replace_forward(const std::string &replacement) {
   Gtk::TextIter match_start, match_end;
   if(gtk_source_search_context_forward(search_context, start.gobj(), match_start.gobj(), match_end.gobj())) {
     auto offset=match_start.get_offset();
-    gtk_source_search_context_replace(search_context, match_start.gobj(), match_end.gobj(), replacement.c_str(), replacement.size(), NULL);
+    gtk_source_search_context_replace(search_context, match_start.gobj(), match_end.gobj(), replacement.c_str(), replacement.size(), nullptr);
     
     Glib::ustring replacement_ustring=replacement;
     get_buffer()->select_range(get_buffer()->get_iter_at_offset(offset), get_buffer()->get_iter_at_offset(offset+replacement_ustring.size()));
@@ -556,7 +556,7 @@ void Source::View::replace_backward(const std::string &replacement) {
   Gtk::TextIter match_start, match_end;
   if(gtk_source_search_context_backward(search_context, start.gobj(), match_start.gobj(), match_end.gobj())) {
     auto offset=match_start.get_offset();
-    gtk_source_search_context_replace(search_context, match_start.gobj(), match_end.gobj(), replacement.c_str(), replacement.size(), NULL);
+    gtk_source_search_context_replace(search_context, match_start.gobj(), match_end.gobj(), replacement.c_str(), replacement.size(), nullptr);
 
     get_buffer()->select_range(get_buffer()->get_iter_at_offset(offset), get_buffer()->get_iter_at_offset(offset+replacement.size()));
     scroll_to(get_buffer()->get_insert());
@@ -564,7 +564,7 @@ void Source::View::replace_backward(const std::string &replacement) {
 }
 
 void Source::View::replace_all(const std::string &replacement) {
-  gtk_source_search_context_replace_all(search_context, replacement.c_str(), replacement.size(), NULL);
+  gtk_source_search_context_replace_all(search_context, replacement.c_str(), replacement.size(), nullptr);
 }
 
 void Source::View::paste() {
diff --git a/src/source_clang.cc b/src/source_clang.cc
index 305d58f..8de43a8 100644
--- a/src/source_clang.cc
+++ b/src/source_clang.cc
@@ -756,7 +756,7 @@ void Source::ClangViewAutocomplete::autocomplete() {
 std::vector<Source::ClangViewAutocomplete::AutoCompleteData> Source::ClangViewAutocomplete::autocomplete_get_suggestions(const std::string &buffer, int line_number, int column) {
   std::vector<AutoCompleteData> suggestions;
   auto results=clang_tu->get_code_completions(buffer, line_number, column);
-  if(results.cx_results==NULL) {
+  if(results.cx_results==nullptr) {
     auto expected=ParseState::PROCESSING;
     parse_state.compare_exchange_strong(expected, ParseState::RESTARTING);
     return suggestions;
@@ -1321,8 +1321,8 @@ void Source::ClangViewRefactor::wait_parsing(const std::vector<Source::View*> &v
   }
   if(message) {
     for(;;) {
-      while(g_main_context_pending(NULL))
-        g_main_context_iteration(NULL, false);
+      while(g_main_context_pending(nullptr))
+        g_main_context_iteration(nullptr, false);
       bool all_parsed=true;
       for(auto &clang_view: clang_views) {
         if(!clang_view->parsed) {
diff --git a/src/source_spellcheck.cc b/src/source_spellcheck.cc
index b5052b2..639b366 100644
--- a/src/source_spellcheck.cc
+++ b/src/source_spellcheck.cc
@@ -16,12 +16,12 @@ namespace sigc {
 #endif
 }
 
-AspellConfig* Source::SpellCheckView::spellcheck_config=NULL;
+AspellConfig* Source::SpellCheckView::spellcheck_config=nullptr;
 
 Source::SpellCheckView::SpellCheckView() : Gsv::View() {
-  if(spellcheck_config==NULL)
+  if(spellcheck_config==nullptr)
     spellcheck_config=new_aspell_config();
-  spellcheck_checker=NULL;
+  spellcheck_checker=nullptr;
   auto tag=get_buffer()->create_tag("spellcheck_error");
   tag->property_underline()=Pango::Underline::UNDERLINE_ERROR;
   
@@ -41,7 +41,7 @@ Source::SpellCheckView::SpellCheckView() : Gsv::View() {
   });
   
   get_buffer()->signal_changed().connect([this](){
-    if(spellcheck_checker==NULL)
+    if(spellcheck_checker==nullptr)
       return;
     
     delayed_spellcheck_suggestions_connection.disconnect();
@@ -131,7 +131,7 @@ Source::SpellCheckView::SpellCheckView() : Gsv::View() {
   });
   
   get_buffer()->signal_mark_set().connect([this](const Gtk::TextBuffer::iterator& iter, const Glib::RefPtr<Gtk::TextBuffer::Mark>& mark) {
-    if(spellcheck_checker==NULL)
+    if(spellcheck_checker==nullptr)
       return;
     
     if(mark->get_name()=="insert") {
@@ -191,7 +191,7 @@ Source::SpellCheckView::~SpellCheckView() {
   delayed_spellcheck_suggestions_connection.disconnect();
   delayed_spellcheck_error_clear.disconnect();
   
-  if(spellcheck_checker!=NULL)
+  if(spellcheck_checker!=nullptr)
     delete_aspell_speller(spellcheck_checker);//asd
 }
 
@@ -201,9 +201,9 @@ void Source::SpellCheckView::configure() {
     aspell_config_replace(spellcheck_config, "encoding", "utf-8");
   }
   spellcheck_possible_err=new_aspell_speller(spellcheck_config);
-  if(spellcheck_checker!=NULL)
+  if(spellcheck_checker!=nullptr)
     delete_aspell_speller(spellcheck_checker);
-  spellcheck_checker=NULL;
+  spellcheck_checker=nullptr;
   if (aspell_error_number(spellcheck_possible_err) != 0)
     std::cerr << "Spell check error: " << aspell_error_message(spellcheck_possible_err) << std::endl;
   else
@@ -218,7 +218,7 @@ void Source::SpellCheckView::hide_dialogs() {
 }
 
 void Source::SpellCheckView::spellcheck(const Gtk::TextIter& start, const Gtk::TextIter& end) {
-  if(spellcheck_checker==NULL)
+  if(spellcheck_checker==nullptr)
     return;
   auto iter=start;
   while(iter && iter<end) {
@@ -353,7 +353,7 @@ std::vector<std::string> Source::SpellCheckView::spellcheck_get_suggestions(cons
   
   std::vector<std::string> words;
   const char *word;
-  while ((word = aspell_string_enumeration_next(elements))!= NULL) {
+  while ((word = aspell_string_enumeration_next(elements))!= nullptr) {
     words.emplace_back(word);
   }
   delete_aspell_string_enumeration(elements);
diff --git a/src/terminal.cc b/src/terminal.cc
index 1e60ac9..45675b4 100644
--- a/src/terminal.cc
+++ b/src/terminal.cc
@@ -334,8 +334,8 @@ void Terminal::clear() {
     for(auto &in_progress: in_progresses)
       in_progress->stop=true;
   }
-  while(g_main_context_pending(NULL))
-    g_main_context_iteration(NULL, false);
+  while(g_main_context_pending(nullptr))
+    g_main_context_iteration(nullptr, false);
   get_buffer()->set_text("");
 }
 
diff --git a/src/window.cc b/src/window.cc
index f150c9d..ae1fa87 100644
--- a/src/window.cc
+++ b/src/window.cc
@@ -513,8 +513,8 @@ void Window::set_menu_actions() {
 #ifdef __APPLE__
                 Terminal::get().process("open \""+uri+"\"");
 #else
-                GError* error=NULL;
-                gtk_show_uri(NULL, uri.c_str(), GDK_CURRENT_TIME, &error);
+                GError* error=nullptr;
+                gtk_show_uri(nullptr, uri.c_str(), GDK_CURRENT_TIME, &error);
                 g_clear_error(&error);
 #endif
               }