diff --git a/lib/rspec/openapi/schema_builder.rb b/lib/rspec/openapi/schema_builder.rb
index 45deda77..9b0d4baa 100644
--- a/lib/rspec/openapi/schema_builder.rb
+++ b/lib/rspec/openapi/schema_builder.rb
@@ -111,7 +111,7 @@ def build_type(value)
     when ActionDispatch::Http::UploadedFile
       { type: 'string', format: 'binary' }
     when NilClass
-      { type: 'null' }
+      { nullable: true }
     else
       raise NotImplementedError, "type detection is not implemented for: #{value.inspect}"
     end
diff --git a/spec/rails/app/controllers/tables_controller.rb b/spec/rails/app/controllers/tables_controller.rb
index 737dbca9..dbe482ea 100644
--- a/spec/rails/app/controllers/tables_controller.rb
+++ b/spec/rails/app/controllers/tables_controller.rb
@@ -47,6 +47,7 @@ def find_table(id = nil)
           id: 2,
           name: 'production',
         },
+        null_sample: nil,
         storage_size: 12.3,
         created_at: time.iso8601,
         updated_at: time.iso8601,
diff --git a/spec/rails/doc/openapi.yaml b/spec/rails/doc/openapi.yaml
index e62076aa..67634be8 100644
--- a/spec/rails/doc/openapi.yaml
+++ b/spec/rails/doc/openapi.yaml
@@ -47,6 +47,8 @@ paths:
                           type: integer
                         name:
                           type: string
+                    null_sample:
+                      nullable: true
                     storage_size:
                       type: number
                       format: float
@@ -61,6 +63,7 @@ paths:
                 database:
                   id: 2
                   name: production
+                null_sample: 
                 storage_size: 12.3
                 created_at: '2020-07-17T00:00:00+00:00'
                 updated_at: '2020-07-17T00:00:00+00:00'
@@ -116,6 +119,8 @@ paths:
                         type: integer
                       name:
                         type: string
+                  null_sample:
+                    nullable: true
                   storage_size:
                     type: number
                     format: float
@@ -130,6 +135,7 @@ paths:
                 database:
                   id: 2
                   name: production
+                null_sample: 
                 storage_size: 12.3
                 created_at: '2020-07-17T00:00:00+00:00'
                 updated_at: '2020-07-17T00:00:00+00:00'
@@ -166,6 +172,8 @@ paths:
                         type: integer
                       name:
                         type: string
+                  null_sample:
+                    nullable: true
                   storage_size:
                     type: number
                     format: float
@@ -180,6 +188,7 @@ paths:
                 database:
                   id: 2
                   name: production
+                null_sample: 
                 storage_size: 12.3
                 created_at: '2020-07-17T00:00:00+00:00'
                 updated_at: '2020-07-17T00:00:00+00:00'
@@ -248,6 +257,8 @@ paths:
                         type: integer
                       name:
                         type: string
+                  null_sample:
+                    nullable: true
                   storage_size:
                     type: number
                     format: float
@@ -262,6 +273,7 @@ paths:
                 database:
                   id: 2
                   name: production
+                null_sample: 
                 storage_size: 12.3
                 created_at: '2020-07-17T00:00:00+00:00'
                 updated_at: '2020-07-17T00:00:00+00:00'
@@ -297,6 +309,8 @@ paths:
                         type: integer
                       name:
                         type: string
+                  null_sample:
+                    nullable: true
                   storage_size:
                     type: number
                     format: float
@@ -311,6 +325,7 @@ paths:
                 database:
                   id: 2
                   name: production
+                null_sample: 
                 storage_size: 12.3
                 created_at: '2020-07-17T00:00:00+00:00'
                 updated_at: '2020-07-17T00:00:00+00:00'