diff --git a/murano/engine/system/heat_stack.py b/murano/engine/system/heat_stack.py
index 004cc782e..090bbd1af 100644
--- a/murano/engine/system/heat_stack.py
+++ b/murano/engine/system/heat_stack.py
@@ -44,7 +44,7 @@ class HeatStack(object):
         self._template = None
         self._parameters = {}
         self._files = {}
-        self._hot_environment = ''
+        self._hot_environment = {}
         self._applied = True
         self._description = description
         self._last_stack_timestamps = (None, None)
diff --git a/murano/tests/unit/test_heat_stack.py b/murano/tests/unit/test_heat_stack.py
index 94a9fe65a..f9ed579a0 100644
--- a/murano/tests/unit/test_heat_stack.py
+++ b/murano/tests/unit/test_heat_stack.py
@@ -62,7 +62,7 @@ class TestHeatStack(base.MuranoTestCase):
         hs = heat_stack.HeatStack('test-stack', 'Generated by TestHeatStack')
         hs._template = {'resources': {'test': 1}}
         hs._files = {}
-        hs._hot_environment = ''
+        hs._hot_environment = {}
         hs._parameters = {}
         hs._applied = False
         hs.push()
@@ -86,7 +86,7 @@ class TestHeatStack(base.MuranoTestCase):
             parameters={},
             template=expected_template,
             files={},
-            environment='',
+            environment={},
             tags=self.mock_tag
         )
         self.assertTrue(hs._applied)