diff --git a/html/index.js b/html/index.js
index 3b49f5f..65ffc49 100644
--- a/html/index.js
+++ b/html/index.js
@@ -171,6 +171,10 @@ async function clickCount() {
 			}
 		}
 		
+		if (evt.data.type === 'stv_exception') {
+			window.alert('An error occurred while counting the votes:\n\n' + evt.data.message);
+		}
+		
 		if (evt.data.type === 'init') {
 			election = evt.data.election;
 			
diff --git a/html/worker.js b/html/worker.js
index afd1b15..c369ede 100644
--- a/html/worker.js
+++ b/html/worker.js
@@ -101,6 +101,10 @@ function stepElection() {
 				// Signals we require input to break a tie
 				postMessage({'type': 'require_input', 'message': ex.message});
 				break;
+			} else if (py.isinstance(ex, py.pyRCV2.method.base_stv.STVException)) {
+				console.error(ex);
+				postMessage({'type': 'stv_exception', 'message': ex.message});
+				break;
 			} else {
 				console.error(ex);
 				throw ex;
diff --git a/pyRCV2/method/base_stv.py b/pyRCV2/method/base_stv.py
index e24120b..ffb167a 100644
--- a/pyRCV2/method/base_stv.py
+++ b/pyRCV2/method/base_stv.py
@@ -49,7 +49,9 @@ def groupby(iterable, keyfunc):
 		return groups
 
 class STVException(Exception):
-	pass
+	def __init__(self, message):
+		Exception.__init__(self)
+		self.message = message
 
 class BaseSTVCounter:
 	"""
@@ -635,7 +637,7 @@ class BaseSTVCounter:
 			if result is not None:
 				return result
 		
-		raise Exception('Unable to resolve tie')
+		raise STVException('Unable to resolve tie')
 	
 	def choose_highest(self, l):
 		"""
@@ -659,7 +661,7 @@ class BaseSTVCounter:
 			if result is not None:
 				return result
 		
-		raise Exception('Unable to resolve tie')
+		raise STVException('Unable to resolve tie')
 	
 	def round_votes(self, num):
 		if self.options['round_votes'] is None: