diff --git a/aegisub/src/ass_dialogue.cpp b/aegisub/src/ass_dialogue.cpp
index 8d7b0f8bc..96b7688cc 100644
--- a/aegisub/src/ass_dialogue.cpp
+++ b/aegisub/src/ass_dialogue.cpp
@@ -46,6 +46,8 @@
 
 #include "ass_dialogue.h"
 #include "ass_override.h"
+#include "compat.h"
+#include "subtitle_format.h"
 #include "utils.h"
 
 AssDialogue::AssDialogue()
@@ -82,7 +84,7 @@ AssDialogue::AssDialogue(wxString const& data)
 , Style("Default")
 {
 	if (!Parse(data))
-		throw "Failed parsing line.";
+		throw SubtitleFormatParseError(STD_STR("Failed parsing line: " + data), 0);
 }
 
 AssDialogue::~AssDialogue () {
diff --git a/aegisub/src/ass_file.cpp b/aegisub/src/ass_file.cpp
index 266e6a636..0d5310569 100644
--- a/aegisub/src/ass_file.cpp
+++ b/aegisub/src/ass_file.cpp
@@ -79,11 +79,9 @@ AssFile::~AssFile() {
 
 /// @brief Load generic subs
 void AssFile::Load(const wxString &_filename, wxString const& charset) {
-	try {
-		// Get proper format reader
-		const SubtitleFormat *reader = SubtitleFormat::GetReader(_filename);
-		if (!reader) throw "Unknown file type";
+	const SubtitleFormat *reader = SubtitleFormat::GetReader(_filename);
 
+	try {
 		AssFile temp;
 		reader->ReadFile(&temp, _filename, charset);
 
diff --git a/aegisub/src/ass_parser.cpp b/aegisub/src/ass_parser.cpp
index 64800f392..24903ae17 100644
--- a/aegisub/src/ass_parser.cpp
+++ b/aegisub/src/ass_parser.cpp
@@ -20,6 +20,7 @@
 #include "ass_dialogue.h"
 #include "ass_file.h"
 #include "ass_style.h"
+#include "subtitle_format.h"
 
 #ifndef AGI_PRE
 #include <wx/log.h>
@@ -83,7 +84,7 @@ void AssParser::ParseScriptInfoLine(wxString const& data) {
 		else if (versionString == "v4.00+")
 			trueVersion = 1;
 		else
-			throw "Unknown SSA file format version";
+			throw SubtitleFormatParseError("Unknown SSA file format version", 0);
 		if (trueVersion != version) {
 			wxLogMessage("Warning: File has the wrong extension.");
 			version = trueVersion;
diff --git a/aegisub/src/ass_style.cpp b/aegisub/src/ass_style.cpp
index 1d05f1cea..4c8902cb8 100644
--- a/aegisub/src/ass_style.cpp
+++ b/aegisub/src/ass_style.cpp
@@ -44,6 +44,7 @@
 #endif
 
 #include "ass_style.h"
+#include "subtitle_format.h"
 #include "utils.h"
 
 AssColor::AssColor () {
@@ -172,21 +173,21 @@ AssStyle::AssStyle()
 }
 
 static wxString get_next_string(wxStringTokenizer &tok) {
-	if (!tok.HasMoreTokens()) throw "Malformed style: not enough fields";
+	if (!tok.HasMoreTokens()) throw SubtitleFormatParseError("Malformed style: not enough fields", 0);
 	return tok.GetNextToken();
 }
 
 static int get_next_int(wxStringTokenizer &tok) {
 	long temp;
 	if (!get_next_string(tok).ToLong(&temp))
-		throw "Malformed style: could not parse int field";
+		throw SubtitleFormatParseError("Malformed style: could not parse int field", 0);
 	return temp;
 }
 
 static double get_next_double(wxStringTokenizer &tok) {
 	double temp;
 	if (!get_next_string(tok).ToDouble(&temp))
-		throw "Malformed style: could not parse double field";
+		throw SubtitleFormatParseError("Malformed style: could not parse double field", 0);
 	return temp;
 }
 
@@ -265,7 +266,7 @@ AssStyle::AssStyle(wxString rawData, int version)
 	encoding = get_next_int(tkn);
 
 	if (tkn.HasMoreTokens())
-		throw "Malformed style: too many fields";
+		throw SubtitleFormatParseError("Malformed style: too many fields", 0);
 
 	UpdateData();
 }
diff --git a/aegisub/src/dialog_style_manager.cpp b/aegisub/src/dialog_style_manager.cpp
index 9cb320a4e..1f564839b 100644
--- a/aegisub/src/dialog_style_manager.cpp
+++ b/aegisub/src/dialog_style_manager.cpp
@@ -600,14 +600,6 @@ void DialogStyleManager::OnCurrentImport() {
 	try {
 		temp.Load(filename);
 	}
-	catch (const char *err) {
-		wxMessageBox(err, "Error", wxOK | wxICON_ERROR | wxCENTER, this);
-		return;
-	}
-	catch (wxString const& err) {
-		wxMessageBox(err, "Error", wxOK | wxICON_ERROR | wxCENTER, this);
-		return;
-	}
 	catch (agi::Exception const& err) {
 		wxMessageBox(lagi_wxString(err.GetChainedMessage()), "Error", wxOK | wxICON_ERROR | wxCENTER, this);
 	}
diff --git a/aegisub/src/frame_main.cpp b/aegisub/src/frame_main.cpp
index 7aac9be37..6300cf42f 100644
--- a/aegisub/src/frame_main.cpp
+++ b/aegisub/src/frame_main.cpp
@@ -455,14 +455,6 @@ void FrameMain::LoadSubtitles(wxString const& filename, wxString const& charset)
 		config::mru->Remove("Subtitle", STD_STR(filename));
 		return;
 	}
-	catch (const char *err) {
-		wxMessageBox(err, "Error", wxOK | wxICON_ERROR | wxCENTER, this);
-		return;
-	}
-	catch (wxString const& err) {
-		wxMessageBox(err, "Error", wxOK | wxICON_ERROR | wxCENTER, this);
-		return;
-	}
 	catch (agi::Exception const& err) {
 		wxMessageBox(lagi_wxString(err.GetChainedMessage()), "Error", wxOK | wxICON_ERROR | wxCENTER, this);
 	}
diff --git a/aegisub/src/subtitle_format.cpp b/aegisub/src/subtitle_format.cpp
index a2a865144..2606d0cdb 100644
--- a/aegisub/src/subtitle_format.cpp
+++ b/aegisub/src/subtitle_format.cpp
@@ -331,21 +331,21 @@ void SubtitleFormat::DestroyFormats() {
 }
 
 template<class Cont, class Pred>
-SubtitleFormat *find_or_null(Cont &container, Pred pred) {
+SubtitleFormat *find_or_throw(Cont &container, Pred pred) {
 	typename Cont::iterator it = find_if(container.begin(), container.end(), pred);
 	if (it == container.end())
-		return 0;
+		throw UnknownSubtitleFormatError("Subtitle format for extension not found", 0);
 	return *it;
 }
 
 const SubtitleFormat *SubtitleFormat::GetReader(wxString const& filename) {
 	LoadFormats();
-	return find_or_null(formats, bind(&SubtitleFormat::CanReadFile, _1, filename));
+	return find_or_throw(formats, bind(&SubtitleFormat::CanReadFile, _1, filename));
 }
 
 const SubtitleFormat *SubtitleFormat::GetWriter(wxString const& filename) {
 	LoadFormats();
-	return find_or_null(formats, bind(&SubtitleFormat::CanWriteFile, _1, filename));
+	return find_or_throw(formats, bind(&SubtitleFormat::CanWriteFile, _1, filename));
 }
 
 wxString SubtitleFormat::GetWildcards(int mode) {
diff --git a/aegisub/src/subtitle_format.h b/aegisub/src/subtitle_format.h
index 6e94a3330..91e90d1c6 100644
--- a/aegisub/src/subtitle_format.h
+++ b/aegisub/src/subtitle_format.h
@@ -146,3 +146,4 @@ public:
 };
 
 DEFINE_SIMPLE_EXCEPTION(SubtitleFormatParseError, agi::InvalidInputException, "subtitle_io/parse/generic")
+DEFINE_SIMPLE_EXCEPTION(UnknownSubtitleFormatError, agi::InvalidInputException, "subtitle_io/unknown")