diff --git a/aegisub/src/subs_edit_ctrl.cpp b/aegisub/src/subs_edit_ctrl.cpp
index 44c5efc59..970acff67 100644
--- a/aegisub/src/subs_edit_ctrl.cpp
+++ b/aegisub/src/subs_edit_ctrl.cpp
@@ -85,6 +85,7 @@ enum {
 SubsTextEditCtrl::SubsTextEditCtrl(wxWindow* parent, wxSize wsize, long style, agi::Context *context)
 : ScintillaTextCtrl(parent, -1, "", wxDefaultPosition, wsize, style)
 , spellchecker(SpellCheckerFactory::GetSpellChecker())
+, thesaurus(agi::util::make_unique<Thesaurus>())
 , context(context)
 {
 	// Set properties
@@ -387,9 +388,6 @@ void SubsTextEditCtrl::AddSpellCheckerEntries(wxMenu &menu) {
 void SubsTextEditCtrl::AddThesaurusEntries(wxMenu &menu) {
 	if (currentWord.empty()) return;
 
-	if (!thesaurus)
-		thesaurus = agi::util::make_unique<Thesaurus>();
-
 	auto results = thesaurus->Lookup(currentWord);
 
 	thesSugs.clear();
diff --git a/aegisub/src/thesaurus.cpp b/aegisub/src/thesaurus.cpp
index d43f689f9..fdececbb6 100644
--- a/aegisub/src/thesaurus.cpp
+++ b/aegisub/src/thesaurus.cpp
@@ -29,6 +29,7 @@
 #include <boost/algorithm/string/case_conv.hpp>
 #include <boost/range/algorithm.hpp>
 
+#include <libaegisub/dispatch.h>
 #include <libaegisub/fs.h>
 #include <libaegisub/log.h>
 #include <libaegisub/path.h>
@@ -99,7 +100,17 @@ void Thesaurus::OnLanguageChanged() {
 
 	LOG_I("thesaurus/file") << "Using thesaurus: " << dat;
 
-	impl = agi::util::make_unique<agi::Thesaurus>(dat, idx);
+	agi::dispatch::Background().Async([=]{
+		try {
+			auto thes = agi::util::make_unique<agi::Thesaurus>(dat, idx);
+			agi::dispatch::Main().Sync([&]{
+				impl = std::move(thes);
+			});
+		}
+		catch (agi::Exception const& e) {
+			LOG_E("thesaurus") << e.GetChainedMessage();
+		}
+	});
 }
 
 void Thesaurus::OnPathChanged() {
diff --git a/aegisub/src/thesaurus.h b/aegisub/src/thesaurus.h
index 4485c5daa..0383cce45 100644
--- a/aegisub/src/thesaurus.h
+++ b/aegisub/src/thesaurus.h
@@ -14,11 +14,6 @@
 //
 // Aegisub Project http://www.aegisub.org/
 
-/// @file thesaurus.h
-/// @see thesaurus.cpp
-/// @ingroup thesaurus
-///
-
 #include <memory>
 #include <string>
 #include <vector>