diff --git a/ext/bg/js/ankiweb.js b/ext/bg/js/ankiweb.js
index bed605ec..41bf74bd 100644
--- a/ext/bg/js/ankiweb.js
+++ b/ext/bg/js/ankiweb.js
@@ -27,7 +27,7 @@ class AnkiWeb {
         return this.retrieve().then(info => {
             const model = info.models.find(m => m.name === note.modelName);
             if (!model) {
-                return Promise.reject('invalid model');
+                return Promise.reject('cannot add note model provided');
             }
 
             const fields = [];
@@ -110,7 +110,7 @@ class AnkiWeb {
 
     static login(username, password) {
         if (username.length === 0 || password.length === 0) {
-            return Promise.reject('unspecified login credentials');
+            return Promise.reject('login credentials not specified');
         }
 
         const data = {username, password, submitted: 1};
@@ -143,7 +143,7 @@ class AnkiWeb {
             }
 
             const xhr = new XMLHttpRequest();
-            xhr.addEventListener('error', () => reject('failed to execute request'));
+            xhr.addEventListener('error', () => reject('failed to execute network request'));
             xhr.addEventListener('load', () => resolve(xhr.responseText));
             xhr.open('GET', url);
             xhr.send();
diff --git a/ext/bg/js/yomichan.js b/ext/bg/js/yomichan.js
index 416a4911..4ba44588 100644
--- a/ext/bg/js/yomichan.js
+++ b/ext/bg/js/yomichan.js
@@ -231,43 +231,43 @@ class Yomichan {
     }
 
     api_getEnabled({callback}) {
-        callback(this.state === 'enabled', null);
+        callback({result: this.state === 'enabled'});
     }
 
     api_getOptions({callback}) {
         loadOptions().then(result => {
-            callback(result, null);
+            callback({result});
         }).catch(error => {
-            callback(null, error);
+            callback({error});
         });
     }
 
     api_findKanji({text, callback}) {
         this.translator.findKanji(text).then(result => {
-            callback(result, null);
+            callback({result});
         }).catch(error => {
-            callback(null, error);
+            callback({error});
         });
     }
 
     api_findTerm({text, callback}) {
         this.translator.findTerm(text).then(result => {
-            callback(result, null);
+            callback({result});
         }).catch(error => {
-            callback(null, error);
+            callback({error});
         });
     }
 
     api_renderText({template, data, callback}) {
-        callback(Handlebars.templates[template](data), null);
+        callback({result: Handlebars.templates[template](data)});
     }
 
     api_addDefinition({definition, mode, callback}) {
         const note = this.formatNote(definition, mode);
         this.anki.addNote(note).then(result => {
-            callback(result, null);
+            callback({result});
         }).catch(error => {
-            callback(null, error);
+            callback({error});
         });
     }
 
@@ -279,22 +279,20 @@ class Yomichan {
             }
         }
 
-        this.anki.canAddNotes(notes).then(results => {
+        this.anki.canAddNotes(notes).then(raw => {
             const states = [];
-            if (results !== null) {
-                for (let resultBase = 0; resultBase < results.length; resultBase += modes.length) {
-                    const state = {};
-                    for (let modeOffset = 0; modeOffset < modes.length; ++modeOffset) {
-                        state[modes[modeOffset]] = results[resultBase + modeOffset];
-                    }
-
-                    states.push(state);
+            for (let resultBase = 0; resultBase < raw.length; resultBase += modes.length) {
+                const state = {};
+                for (let modeOffset = 0; modeOffset < modes.length; ++modeOffset) {
+                    state[modes[modeOffset]] = raw[resultBase + modeOffset];
                 }
+
+                states.push(state);
             }
 
-            callback(states, null);
+            callback({result: states});
         }).catch(error => {
-            callback(null, error);
+            callback({error});
         });
     }
 }
diff --git a/ext/fg/js/driver.js b/ext/fg/js/driver.js
index 75dbe219..9aab7950 100644
--- a/ext/fg/js/driver.js
+++ b/ext/fg/js/driver.js
@@ -163,6 +163,8 @@ class Driver {
                     return true;
                 });
             }
+        }).catch(error => {
+            alert('Error: ' + error);
         });
     }
 
@@ -202,6 +204,8 @@ class Driver {
                     return true;
                 });
             }
+        }).catch(error => {
+            alert('Error: ' + error);
         });
     }
 
@@ -231,6 +235,8 @@ class Driver {
                     }
                 });
             }
+        }).catch(error => {
+            alert('Error: ' + error);
         });
     }
 
@@ -273,6 +279,8 @@ class Driver {
             } else {
                 alert('Note could not be added');
             }
+        }).catch(error => {
+            alert('Error: ' + error);
         });
     }
 
@@ -317,6 +325,8 @@ class Driver {
                     states.forEach((state, index) => this.popup.invokeApi('setActionState', {index, state, sequence}));
                 }
             });
+        }).catch(error => {
+            alert('Error: ' + error);
         });
     }
 }
diff --git a/ext/fg/js/util.js b/ext/fg/js/util.js
index 7248ae86..6f2fd28d 100644
--- a/ext/fg/js/util.js
+++ b/ext/fg/js/util.js
@@ -19,7 +19,7 @@
 
 function invokeApiBg(action, params) {
     return new Promise((resolve, reject) => {
-        chrome.runtime.sendMessage({action, params}, (result, error) => {
+        chrome.runtime.sendMessage({action, params}, ({result, error}) => {
             if (error) {
                 reject(error);
             } else {