diff --git a/superset/utils.py b/superset/utils.py
index 42f2da3aaf031..469bbc26cfc7a 100644
--- a/superset/utils.py
+++ b/superset/utils.py
@@ -668,8 +668,8 @@ def get_celery_app(config):
 def merge_extra_filters(form_data):
     # extra_filters are temporary/contextual filters that are external
     # to the slice definition. We use those for dynamic interactive
-    # filters like the ones emitted by the 'Filter Box' visualization
-    if form_data.get('extra_filters'):
+    # filters like the ones emitted by the "Filter Box" visualization
+    if 'extra_filters' in form_data:
         # __form and __to are special extra_filters that target time
         # boundaries. The rest of extra_filters are simple
         # [column_name in list_of_values]. `__` prefix is there to avoid
diff --git a/superset/viz.py b/superset/viz.py
index e1ebe742d4a0a..8a90c81868b08 100644
--- a/superset/viz.py
+++ b/superset/viz.py
@@ -220,7 +220,9 @@ def get_json(self, force=False):
 
     @property
     def cache_key(self):
-        s = str([(k, self.form_data[k]) for k in sorted(self.form_data.keys())])
+        form_data = self.form_data.copy()
+        merge_extra_filters(form_data)
+        s = str([(k, form_data[k]) for k in sorted(form_data.keys())])
         return hashlib.md5(s.encode('utf-8')).hexdigest()
 
     def get_annotations(self):
diff --git a/tests/utils_tests.py b/tests/utils_tests.py
index 1d5cc65fab1c8..f6d1901d120d4 100644
--- a/tests/utils_tests.py
+++ b/tests/utils_tests.py
@@ -61,9 +61,9 @@ def test_merge_extra_filters(self):
         expected = {'A': 1, 'B': 2, 'c': 'test'}
         merge_extra_filters(form_data)
         self.assertEquals(form_data, expected)
-        # does nothing if empty extra_filters
+        # empty extra_filters
         form_data = {'A': 1, 'B': 2, 'c': 'test', 'extra_filters': []}
-        expected = {'A': 1, 'B': 2, 'c': 'test', 'extra_filters': []}
+        expected = {'A': 1, 'B': 2, 'c': 'test', 'filters': []}
         merge_extra_filters(form_data)
         self.assertEquals(form_data, expected)
         # copy over extra filters into empty filters