diff --git a/python/plugins/processing/core/parameters.py b/python/plugins/processing/core/parameters.py
index b379cd8359c..03b458b6333 100644
--- a/python/plugins/processing/core/parameters.py
+++ b/python/plugins/processing/core/parameters.py
@@ -1191,7 +1191,7 @@ class ParameterString(Parameter):
         if self.optional:
             param_type += 'optional '
         param_type += 'string '
-        return '##' + self.name + '=' + param_type + str(self.default)
+        return '##' + self.name + '=' + param_type + repr(self.default)
 
     @classmethod
     def fromScriptCode(self, line):
@@ -1201,6 +1201,8 @@ class ParameterString(Parameter):
             default = definition.strip()[len('string') + 1:] or None
             if default == 'None':
                 default = None
+            elif default.startswith('"') or default.startswith('\''):
+                default = eval(default)
             if default:
                 return ParameterString(name, descName, default, optional=isOptional)
             else:
diff --git a/python/plugins/processing/tests/ParametersTest.py b/python/plugins/processing/tests/ParametersTest.py
index cdcb4b79a8c..08ae80d7f74 100644
--- a/python/plugins/processing/tests/ParametersTest.py
+++ b/python/plugins/processing/tests/ParametersTest.py
@@ -593,12 +593,29 @@ class ParameterStringTest(unittest.TestCase):
         code = parameter.getAsScriptCode()
         result = getParameterFromString(code)
         self.assertIsInstance(result, ParameterString)
+        self.assertEqual(result.default, parameter.default)
 
+        parameter.default = None
         parameter.optional = True
         code = parameter.getAsScriptCode()
         result = getParameterFromString(code)
         self.assertIsInstance(result, ParameterString)
         self.assertTrue(result.optional)
+        self.assertEqual(result.default, parameter.default)
+
+        parameter.default = 'None'
+        code = parameter.getAsScriptCode()
+        result = getParameterFromString(code)
+        self.assertIsInstance(result, ParameterString)
+        self.assertTrue(result.optional)
+        self.assertEqual(result.default, parameter.default)
+
+        parameter.default = 'It\'s Mario'
+        code = parameter.getAsScriptCode()
+        result = getParameterFromString(code)
+        self.assertIsInstance(result, ParameterString)
+        self.assertTrue(result.optional)
+        self.assertEqual(result.default, parameter.default)
 
 
 class ParameterExpressionTest(unittest.TestCase):