diff --git a/docker/services/ceph-ansible/ceph-base.yaml b/docker/services/ceph-ansible/ceph-base.yaml
index d589687fd6..c9d3280736 100644
--- a/docker/services/ceph-ansible/ceph-base.yaml
+++ b/docker/services/ceph-ansible/ceph-base.yaml
@@ -39,9 +39,9 @@ parameters:
     - allowed_values: ['', 'UPGRADE', 'FASTFORWARDUPGRADE']
     default: ''
   NodeDataLookup:
-    type: string
-    default: '{}'
-    description: json string containing per-node configuration map
+    type: json
+    default: {}
+    description: json containing per-node configuration map
   DeploymentServerBlacklist:
     default: []
     type: comma_delimited_list
diff --git a/puppet/extraconfig/pre_deploy/per_node.yaml b/puppet/extraconfig/pre_deploy/per_node.yaml
index 37a72cf43b..5e79748108 100644
--- a/puppet/extraconfig/pre_deploy/per_node.yaml
+++ b/puppet/extraconfig/pre_deploy/per_node.yaml
@@ -12,13 +12,13 @@ parameters:
   # to the json required for the node-specific hieradata
   # Note this needs to be a json blob e.g:
   #      parameter_defaults:
-  #        NodeDataLookup: |
+  #        NodeDataLookup:
   #          {"AB4114B1-9C9D-409A-BEFB-D88C151BF2C3": {"foo": "bar"},
   #           "8CF1A7EA-7B4B-4433-AC83-17675514B1B8": {"foo2": "bar2"}}
   NodeDataLookup:
-    type: string
-    default: '{}'
-    description: json string containing per-node configuration map
+    type: json
+    default: {}
+    description: json containing per-node configuration map
 
 resources:
   NodeSpecificConfig:
diff --git a/releasenotes/notes/node_data_lookup_string_to_json-69362e93d862bd87.yaml b/releasenotes/notes/node_data_lookup_string_to_json-69362e93d862bd87.yaml
new file mode 100644
index 0000000000..361d2e7401
--- /dev/null
+++ b/releasenotes/notes/node_data_lookup_string_to_json-69362e93d862bd87.yaml
@@ -0,0 +1,7 @@
+---
+deprecations:
+  - |
+    The NodeDataLookup parameter type was changed from string to json
+fixes:
+  - |
+    - Bug 1784967 invalid JSON in NodeDataLookup error message should be more helpful