diff --git a/filters.js b/filters.js
index 3ea8e75b8..4054fb28c 100644
--- a/filters.js
+++ b/filters.js
@@ -40,7 +40,7 @@ var filters = {
     'minus': bindFixed((v, arg) => v - arg),
     'modulo': bindFixed((v, arg) => v % arg),
     'newline_to_br': v => v.replace(/\n/g, '<br />'),
-    'plus': bindFixed((v, arg) => v + arg),
+    'plus': bindFixed((v, arg) => Number(v) + Number(arg)),
     'prepend': (v, arg) => arg + v,
     'remove': (v, arg) => v.split(arg).join(''),
     'remove_first': (v, l) => v.replace(l, ''),
diff --git a/test/filters.js b/test/filters.js
index 0aef8554b..80adf457e 100644
--- a/test/filters.js
+++ b/test/filters.js
@@ -133,6 +133,7 @@ describe('filters', function() {
         it('should return "12" for 16,4', () => test('{{ 16 | minus: 4 }}', '12'));
         it('should return "171.357" for 183.357,12',
             () => test('{{ 183.357 | minus: 12 }}', '171.357'));
+        it('should convert string to number', () => test('{{ "4" | minus: 1 }}', '3'));
     });
 
     describe('modulo', function() {
@@ -159,6 +160,7 @@ describe('filters', function() {
         it('should return "20" for 16,4', () => test('{{ 16 | plus: 4 }}', '20'));
         it('should return "195.357" for 183.357,12',
             () => test('{{ 183.357 | plus: 12 }}', '195.357'));
+        it('should convert string to number', () => test('{{ "4" | plus: 2 }}', '6'));
     });
 
     it('should support prepend', function() {