diff --git a/heat/engine/software_config_io.py b/heat/engine/software_config_io.py
index 5685fc3b79..8ca2d28f7b 100644
--- a/heat/engine/software_config_io.py
+++ b/heat/engine/software_config_io.py
@@ -129,11 +129,16 @@ class InputConfig(IOConfig):
 
     def __init__(self, value=_no_value, **config):
         if TYPE in config and DEFAULT in config:
-            self.schema = copy.deepcopy(self.schema)
-            config_param = parameters.Schema.from_dict(
-                'config', {'Type': config[TYPE]})
-            self.schema[DEFAULT] = properties.Schema.from_parameter(
-                config_param)
+            if config[DEFAULT] == '' and config[TYPE] != STRING_TYPE:
+                # This is a legacy path, because default used to be of string
+                # type, so we need to skip schema validation in this case.
+                pass
+            else:
+                self.schema = copy.deepcopy(self.schema)
+                config_param = parameters.Schema.from_dict(
+                    'config', {'Type': config[TYPE]})
+                self.schema[DEFAULT] = properties.Schema.from_parameter(
+                    config_param)
         super(InputConfig, self).__init__(**config)
         self._value = value
 
diff --git a/heat/tests/engine/service/test_software_config.py b/heat/tests/engine/service/test_software_config.py
index ee474b9f02..c99d15565e 100644
--- a/heat/tests/engine/service/test_software_config.py
+++ b/heat/tests/engine/service/test_software_config.py
@@ -1058,3 +1058,11 @@ class SoftwareConfigIOSchemaTest(common.HeatTestCase):
         inp = swc_io.InputConfig(name=name, type='Number',
                                  default='0')
         self.assertEqual(0, inp.default())
+
+    def test_input_config_value_ignore_string(self):
+        name = 'baz'
+        inp = swc_io.InputConfig(name=name, type='Number',
+                                 default='')
+
+        self.assertEqual({'type': 'Number', 'name': 'baz', 'default': ''},
+                         inp.as_dict())