diff --git a/src/columns/ColUDA.cpp b/src/columns/ColUDA.cpp
index fb003c8bb..9f00cc895 100644
--- a/src/columns/ColUDA.cpp
+++ b/src/columns/ColUDA.cpp
@@ -57,6 +57,23 @@ ColumnUDA::~ColumnUDA ()
 {
 }
 
+////////////////////////////////////////////////////////////////////////////////
+bool ColumnUDA::validate (std::string& value)
+{
+  // No restrictions.
+  if (_values.size () == 0)
+    return true;
+
+  // Look for exact match value.
+  std::vector <std::string>::iterator i;
+  for (i = _values.begin (); i != _values.end (); ++i)
+    if (*i == value)
+      return true;
+
+  // Fail if not found.
+  return false;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Set the minimum and maximum widths for the value.
 //
diff --git a/src/columns/ColUDA.h b/src/columns/ColUDA.h
index 7a8e13e12..29ff9a80b 100644
--- a/src/columns/ColUDA.h
+++ b/src/columns/ColUDA.h
@@ -41,9 +41,13 @@ public:
   ColumnUDA ();
   ~ColumnUDA ();
 
+  bool validate (std::string&);
   void measure (Task&, int&, int&);
   void render (std::vector <std::string>&, Task&, int, Color&);
 
+public:
+  std::vector <std::string> _values;
+
 private:
   bool _hyphenate;
 };
diff --git a/src/columns/Column.cpp b/src/columns/Column.cpp
index ba131f3bf..599116e28 100644
--- a/src/columns/Column.cpp
+++ b/src/columns/Column.cpp
@@ -181,7 +181,7 @@ void Column::uda (std::map <std::string, Column*>& all)
 ////////////////////////////////////////////////////////////////////////////////
 Column* Column::uda (const std::string& name)
 {
-  Column* c = new ColumnUDA ();
+  ColumnUDA* c = new ColumnUDA ();
   c->_name = name;
 
   std::string key = "uda." + name + ".type";
@@ -195,6 +195,11 @@ Column* Column::uda (const std::string& name)
   key = "uda." + name + ".label";
   if (context.config.get (key) != "")
     c->_label = context.config.get (key);
+
+  key = "uda." + name + ".values";
+  if (context.config.get (key) != "")
+    split (c->_values, context.config.get (key), ',');
+
   return c;
 }
 
diff --git a/src/commands/Command.cpp b/src/commands/Command.cpp
index cc29f234a..61b83b7f2 100644
--- a/src/commands/Command.cpp
+++ b/src/commands/Command.cpp
@@ -596,7 +596,12 @@ void Command::modify_task (
 
           // By default, just add/remove it.
           else
-            task.set (name, value);
+          {
+            if (column->validate (value))
+              task.set (name, value);
+            else
+              throw format (STRING_INVALID_MOD, name, value);
+          }
 
           // Warn about deprecated/obsolete attribute usage.
           legacyAttributeCheck (name);
diff --git a/src/en-US.h b/src/en-US.h
index 0b63168fb..104168c31 100644
--- a/src/en-US.h
+++ b/src/en-US.h
@@ -683,6 +683,7 @@
 #define STRING_INFINITE_LOOP         "Terminated substitution because more than {1} changes were made - infinite loop protection."
 #define STRING_UDA_TYPE              "User defined attributes may only be of type 'string', 'date', 'duration' or 'numeric'."
 #define STRING_UDA_NUMERIC           "The value '{1}' is not a valid numeric value."
+#define STRING_INVALID_MOD           "The '{1}' attribute does not allow a value of '{2}'."
 
 // Feedback
 #define STRING_FEEDBACK_NO_TASKS     "No tasks."