diff --git a/dropshot/src/api_description.rs b/dropshot/src/api_description.rs
index 228c3e4eb..bafe1442f 100644
--- a/dropshot/src/api_description.rs
+++ b/dropshot/src/api_description.rs
@@ -778,15 +778,32 @@ impl<Context: ServerContext> ApiDescription<Context> {
             } else {
                 // If no schema was specified, the response is hand-rolled. In
                 // this case we'll fall back to the default response type which
-                // we assume to be inclusive of errors.
+                // we assume to be inclusive of errors. The media type and
+                // and schema will similarly be maximally permissive.
+                let mut content = indexmap::IndexMap::new();
+                content.insert(
+                    "*/*".to_string(),
+                    openapiv3::MediaType {
+                        schema: Some(openapiv3::ReferenceOr::Item(
+                            openapiv3::Schema {
+                                schema_data: openapiv3::SchemaData::default(),
+                                schema_kind: openapiv3::SchemaKind::Any(
+                                    openapiv3::AnySchema::default(),
+                                ),
+                            },
+                        )),
+                        ..Default::default()
+                    },
+                );
                 operation.responses.default =
                     Some(openapiv3::ReferenceOr::Item(openapiv3::Response {
                         // TODO: perhaps we should require even free-form
                         // responses to have a description since it's required
                         // by OpenAPI.
                         description: "".to_string(),
+                        content,
                         ..Default::default()
-                    }))
+                    }));
             }
 
             // Drop in the operation.
diff --git a/dropshot/tests/test_openapi.json b/dropshot/tests/test_openapi.json
index ebf639c01..7b5563d36 100644
--- a/dropshot/tests/test_openapi.json
+++ b/dropshot/tests/test_openapi.json
@@ -485,7 +485,12 @@
         "operationId": "handler16",
         "responses": {
           "default": {
-            "description": ""
+            "description": "",
+            "content": {
+              "*/*": {
+                "schema": {}
+              }
+            }
           }
         }
       }
diff --git a/dropshot/tests/test_openapi_fuller.json b/dropshot/tests/test_openapi_fuller.json
index 6c376e639..4e9bd4988 100644
--- a/dropshot/tests/test_openapi_fuller.json
+++ b/dropshot/tests/test_openapi_fuller.json
@@ -493,7 +493,12 @@
         "operationId": "handler16",
         "responses": {
           "default": {
-            "description": ""
+            "description": "",
+            "content": {
+              "*/*": {
+                "schema": {}
+              }
+            }
           }
         }
       }