diff --git a/common/content/dactyl.js b/common/content/dactyl.js
index b8c95ef4..916dd18e 100644
--- a/common/content/dactyl.js
+++ b/common/content/dactyl.js
@@ -1183,7 +1183,8 @@ const Dactyl = Module("dactyl", {
                     options.safeSetPref("layout.scrollbar.side", opts.indexOf("l") >= 0 ? 3 : 2,
                                         "See 'guioptions' scrollbar flags.");
                 },
-                validator: function (opts) (opts.indexOf("l") < 0 || opts.indexOf("r") < 0)
+                validator: function (opts) Option.validIf(!(opts.indexOf("l") >= 0 && opts.indexOf("r") >= 0),
+                                                          UTF8("Only one of ‘l’ or ‘r’ allowed"))
             },
             tab: {
                 feature: "tabs",
@@ -1271,7 +1272,7 @@ const Dactyl = Module("dactyl", {
         options.add(["verbose", "vbs"],
             "Define which info messages are displayed",
             "number", 1,
-            { validator: function (value) value >= 0 && value <= 15 });
+            { validator: function (value) Option.validIf(value >= 0 && value <= 15, "Value must be between 0 and 15") });
 
         options.add(["visualbell", "vb"],
             "Use visual bell instead of beeping on errors",
diff --git a/common/content/hints.js b/common/content/hints.js
index 6fb546c6..b1d91a98 100644
--- a/common/content/hints.js
+++ b/common/content/hints.js
@@ -1072,7 +1072,8 @@ const Hints = Module("hints", {
                     ["asdfg;lkjh", "Home Row"]],
                 validator: function (value) {
                     let values = events.fromString(value).map(events.closure.toString);
-                    return array.uniq(values).length === values.length;
+                    return Option.validIf(array.uniq(values).length === values.length,
+                                          "Duplicate keys not allowed")
                 }
             });
 
diff --git a/common/content/options.js b/common/content/options.js
index 63613df5..01a4f869 100644
--- a/common/content/options.js
+++ b/common/content/options.js
@@ -234,8 +234,13 @@ const Option = Class("Option", {
         if (newValues == null)
             return "Operator " + operator + " not supported for option type " + this.type;
 
-        if (!this.isValidValue(newValues))
-            return this.invalidArgument(str || this.joinValues(values), operator);
+        try {
+            if (!this.isValidValue(newValues))
+                return this.invalidArgument(str || this.joinValues(values), operator);
+        }
+        catch (e) {
+            return this.invalidArgument(str || this.joinValues(values), operator) + ": " + e.message;
+        }
 
         this.setValues(newValues, scope);
         return null;
@@ -551,6 +556,12 @@ const Option = Class("Option", {
         }
     },
 
+    validIf: function (test, error) {
+        if (test)
+            return true;
+        throw Error(error);
+    },
+
     // TODO: Run this by default?
     /**
      * Validates the specified <b>values</b> against values generated by the