diff --git a/cloudkittyclient/v1/rating/hashmap.py b/cloudkittyclient/v1/rating/hashmap.py
index 85c02ca..ba56dc2 100644
--- a/cloudkittyclient/v1/rating/hashmap.py
+++ b/cloudkittyclient/v1/rating/hashmap.py
@@ -172,7 +172,7 @@ class HashmapManager(base.BaseManager):
         :param value: Value of the mapping
         :type value: str
         """
-        if not kwargs.get('cost'):
+        if kwargs.get('cost') is None:
             raise exc.ArgumentRequired("'cost' argument is required")
         if not kwargs.get('value'):
             if not kwargs.get('service_id'):
diff --git a/releasenotes/notes/fix-zero-cost-mapping-7a4247cf1c6815f8.yaml b/releasenotes/notes/fix-zero-cost-mapping-7a4247cf1c6815f8.yaml
new file mode 100644
index 0000000..c73d1a5
--- /dev/null
+++ b/releasenotes/notes/fix-zero-cost-mapping-7a4247cf1c6815f8.yaml
@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Fixes creation of hashmap mappings with a zero cost.