diff --git a/src/ApiGenerator/RestSpecification/Core/close_point_in_time.json b/src/ApiGenerator/RestSpecification/Core/close_point_in_time.json
index d3f636a1bd0..c25ac88847d 100644
--- a/src/ApiGenerator/RestSpecification/Core/close_point_in_time.json
+++ b/src/ApiGenerator/RestSpecification/Core/close_point_in_time.json
@@ -7,7 +7,8 @@
     "stability":"stable",
     "visibility":"public",
     "headers":{
-      "accept": [ "application/json"]
+      "accept": [ "application/json"],
+      "content_type": ["application/json"]
     },
     "url":{
       "paths":[
diff --git a/src/ApiGenerator/RestSpecification/Core/field_caps.json b/src/ApiGenerator/RestSpecification/Core/field_caps.json
index d2632a12676..f1f5e3992ab 100644
--- a/src/ApiGenerator/RestSpecification/Core/field_caps.json
+++ b/src/ApiGenerator/RestSpecification/Core/field_caps.json
@@ -7,7 +7,8 @@
     "stability":"stable",
     "visibility":"public",
     "headers":{
-      "accept": [ "application/json"]
+      "accept": [ "application/json"],
+      "content_type": ["application/json"]
     },
     "url":{
       "paths":[
diff --git a/src/ApiGenerator/RestSpecification/Core/ml.delete_expired_data.json b/src/ApiGenerator/RestSpecification/Core/ml.delete_expired_data.json
index c45ca323d40..f2e8446934c 100644
--- a/src/ApiGenerator/RestSpecification/Core/ml.delete_expired_data.json
+++ b/src/ApiGenerator/RestSpecification/Core/ml.delete_expired_data.json
@@ -7,7 +7,8 @@
     "stability":"stable",
     "visibility":"public",
     "headers":{
-      "accept": [ "application/json"]
+      "accept": [ "application/json"],
+      "content_type": ["application/json"]
     },
     "url":{
       "paths":[
diff --git a/src/ApiGenerator/RestSpecification/Core/ml.preview_datafeed.json b/src/ApiGenerator/RestSpecification/Core/ml.preview_datafeed.json
index 2077cc5d396..8f4486ed1b2 100644
--- a/src/ApiGenerator/RestSpecification/Core/ml.preview_datafeed.json
+++ b/src/ApiGenerator/RestSpecification/Core/ml.preview_datafeed.json
@@ -7,7 +7,8 @@
     "stability":"stable",
     "visibility":"public",
     "headers":{
-      "accept": [ "application/json"]
+      "accept": [ "application/json"],
+      "content_type": ["application/json"]
     },
     "url":{
       "paths":[
diff --git a/src/ApiGenerator/RestSpecification/Core/ml.stop_datafeed.json b/src/ApiGenerator/RestSpecification/Core/ml.stop_datafeed.json
index 5dca1e79703..f689a33d72c 100644
--- a/src/ApiGenerator/RestSpecification/Core/ml.stop_datafeed.json
+++ b/src/ApiGenerator/RestSpecification/Core/ml.stop_datafeed.json
@@ -7,7 +7,8 @@
     "stability":"stable",
     "visibility":"public",
     "headers":{
-      "accept": [ "application/json"]
+      "accept": [ "application/json"],
+      "content_type": ["application/json"]
     },
     "url":{
       "paths":[