diff --git a/VERSION b/VERSION
index 1892b92..31e5c84 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.3.2
+1.3.3
diff --git a/app/app.py b/app/app.py
index 36e1ad3..9976ac0 100644
--- a/app/app.py
+++ b/app/app.py
@@ -112,6 +112,9 @@ def create_app(args):
     if not args.disable_files_translation:
         remove_translated_files.setup(get_upload_dir())
     languages = load_languages()
+    language_pairs = {}
+    for lang in languages:
+        language_pairs[lang.code] = sorted([l.to_lang.code for l in lang.translations_from])
 
     # Map userdefined frontend languages to argos language object.
     if args.frontend_language_source == "auto":
@@ -269,17 +272,13 @@ def create_app(args):
                   name:
                     type: string
                     description: Human-readable language name (in English)
-          429:
-            description: Slow down
-            schema:
-              id: error-slow-down
-              type: object
-              properties:
-                error:
-                  type: string
-                  description: Reason for slow down
+                  targets:
+                    type: array
+                    items:
+                      type: string
+                    description: Supported target language codes
         """
-        return jsonify([{"code": l.code, "name": l.name} for l in languages])
+        return jsonify([{"code": l.code, "name": l.name, "targets": language_pairs.get(l.code, [])} for l in languages])
 
     # Add cors
     @app.after_request
@@ -486,6 +485,9 @@ def create_app(args):
                 results = []
                 for idx, text in enumerate(q):
                     translator = src_langs[idx].get_translation(tgt_lang)
+                    if translator is None:
+                        abort(400, description="%s (%s) is not available as a target language from %s (%s)" % (tgt_lang.name, tgt_lang.code, src_langs[idx].name, src_langs[idx].code))
+
                     if text_format == "html":
                         translated_text = str(translate_html(translator, text))
                     else:
@@ -501,12 +503,14 @@ def create_app(args):
                     )
                 else:
                     return jsonify(
-                         {
+                          {
                             "translatedText": results
-                         }
+                          }
                     )
             else:
                 translator = src_langs[0].get_translation(tgt_lang)
+                if translator is None:
+                    abort(400, description="%s (%s) is not available as a target language from %s (%s)" % (tgt_lang.name, tgt_lang.code, src_langs[0].name, src_langs[0].code))
 
                 if text_format == "html":
                     translated_text = str(translate_html(translator, q))
@@ -517,7 +521,7 @@ def create_app(args):
                     return jsonify(
                         {
                             "translatedText": unescape(translated_text),
-						    "detectedLanguage": source_langs[0]
+                            "detectedLanguage": source_langs[0]
                         }
                     )
                 else:
@@ -940,7 +944,7 @@ def create_app(args):
         return jsonify({"success": True})
 
     swag = swagger(app)
-    swag["info"]["version"] = "1.3.0"
+    swag["info"]["version"] = "1.3.1"
     swag["info"]["title"] = "LibreTranslate"
 
     @app.route("/spec")
diff --git a/app/language.py b/app/language.py
index a19ad2f..2e358c2 100644
--- a/app/language.py
+++ b/app/language.py
@@ -83,7 +83,10 @@ def improve_translation_formatting(source, translation, improve_punctuation=True
 
     if not len(source):
         return ""
-
+    
+    if not len(translation):
+        return source
+    
     if improve_punctuation:
         source_last_char = source[len(source) - 1]
         translation_last_char = translation[len(translation) - 1]
diff --git a/app/static/css/main.css b/app/static/css/main.css
index 9a0ce4b..7ee8554 100644
--- a/app/static/css/main.css
+++ b/app/static/css/main.css
@@ -61,14 +61,6 @@ h3.header {
   position: relative;
 }
 
-@-moz-document url-prefix() {
-  .language-select select {
-    -moz-appearance: none;
-    text-indent: -2px;
-    margin-right: -8px;
-  }
-}
-
 .language-select:after {
   content: "";
   width: 0.5em;
diff --git a/app/static/js/app.js b/app/static/js/app.js
index cd53e0e..d32b140 100644
--- a/app/static/js/app.js
+++ b/app/static/js/app.js
@@ -141,8 +141,16 @@ document.addEventListener('DOMContentLoaded', function(){
             isHtml: function(){
                 return htmlRegex.test(this.inputText);
             },
-            canSendSuggestion() {
+            canSendSuggestion: function(){
                 return this.translatedText.trim() !== "" && this.translatedText !== this.savedTanslatedText;
+            },
+            targetLangs: function(){
+                if (!this.sourceLang) return this.langs;
+                else{
+                    var lang = this.langs.find(l => l.code === this.sourceLang);
+                    if (!lang) return this.langs;
+                    return lang.targets.map(t => this.langs.find(l => l.code === t));
+                }
             }
         },
         filters: {
@@ -161,7 +169,13 @@ document.addEventListener('DOMContentLoaded', function(){
                 }
             },
             swapLangs: function(e){
-                this.closeSuggestTranslation(e)
+                this.closeSuggestTranslation(e);
+
+                // Make sure that we can swap
+                // by checking that the current target language
+                // has source language as target
+                var tgtLang = this.langs.find(l => l.code === this.targetLang);
+                if (tgtLang.targets.indexOf(this.sourceLang) === -1) return; // Not supported
 
                 var t = this.sourceLang;
                 this.sourceLang = this.targetLang;
diff --git a/app/templates/index.html b/app/templates/index.html
index e9068ea..396754f 100644
--- a/app/templates/index.html
+++ b/app/templates/index.html
@@ -156,7 +156,7 @@
 								</a>
 								<span>Translate into</span>
 								<select class="browser-default" v-model="targetLang" ref="targetLangDropdown" @change="handleInput">
-									<template v-for="option in langs">
+									<template v-for="option in targetLangs">
 										<option v-if="option.code !== 'auto'" :value="option.code">[[ option.name ]]</option>
 									</template>
 								</select>