diff --git a/modules/openapi-generator/src/main/resources/r/ApiResponse.mustache b/modules/openapi-generator/src/main/resources/r/ApiResponse.mustache
index 058bdb5ca280..28520f752bef 100644
--- a/modules/openapi-generator/src/main/resources/r/ApiResponse.mustache
+++ b/modules/openapi-generator/src/main/resources/r/ApiResponse.mustache
@@ -50,6 +50,9 @@ ApiResponse <- R6::R6Class(
     #' @param to_encoding The target encoding of the return value.
     #' @export
     response_as_text = function(from_encoding = "", to_encoding = "UTF-8") {
+      if (is.null(self$response)) {
+        self$response <- charToRaw(jsonlite::toJSON("NULL"))
+      }
       text_response <- iconv(readBin(self$response, character()), from = from_encoding, to = to_encoding)
       if (is.na(text_response)) {
         warning("The response is binary and will not be converted to text.")
diff --git a/samples/client/echo_api/r/R/api_response.R b/samples/client/echo_api/r/R/api_response.R
index 404f2ec8a9e8..999532bf3611 100644
--- a/samples/client/echo_api/r/R/api_response.R
+++ b/samples/client/echo_api/r/R/api_response.R
@@ -57,6 +57,9 @@ ApiResponse <- R6::R6Class(
     #' @param to_encoding The target encoding of the return value.
     #' @export
     response_as_text = function(from_encoding = "", to_encoding = "UTF-8") {
+      if (is.null(self$response)) {
+        self$response <- charToRaw(jsonlite::toJSON("NULL"))
+      }
       text_response <- iconv(readBin(self$response, character()), from = from_encoding, to = to_encoding)
       if (is.na(text_response)) {
         warning("The response is binary and will not be converted to text.")
diff --git a/samples/client/petstore/R-httr2-wrapper/R/api_response.R b/samples/client/petstore/R-httr2-wrapper/R/api_response.R
index b84d66f6ee0f..2916fd07d45a 100644
--- a/samples/client/petstore/R-httr2-wrapper/R/api_response.R
+++ b/samples/client/petstore/R-httr2-wrapper/R/api_response.R
@@ -56,6 +56,9 @@ ApiResponse <- R6::R6Class(
     #' @param to_encoding The target encoding of the return value.
     #' @export
     response_as_text = function(from_encoding = "", to_encoding = "UTF-8") {
+      if (is.null(self$response)) {
+        self$response <- charToRaw(jsonlite::toJSON("NULL"))
+      }
       text_response <- iconv(readBin(self$response, character()), from = from_encoding, to = to_encoding)
       if (is.na(text_response)) {
         warning("The response is binary and will not be converted to text.")
diff --git a/samples/client/petstore/R-httr2/R/api_response.R b/samples/client/petstore/R-httr2/R/api_response.R
index b84d66f6ee0f..2916fd07d45a 100644
--- a/samples/client/petstore/R-httr2/R/api_response.R
+++ b/samples/client/petstore/R-httr2/R/api_response.R
@@ -56,6 +56,9 @@ ApiResponse <- R6::R6Class(
     #' @param to_encoding The target encoding of the return value.
     #' @export
     response_as_text = function(from_encoding = "", to_encoding = "UTF-8") {
+      if (is.null(self$response)) {
+        self$response <- charToRaw(jsonlite::toJSON("NULL"))
+      }
       text_response <- iconv(readBin(self$response, character()), from = from_encoding, to = to_encoding)
       if (is.na(text_response)) {
         warning("The response is binary and will not be converted to text.")
diff --git a/samples/client/petstore/R/R/api_response.R b/samples/client/petstore/R/R/api_response.R
index b84d66f6ee0f..2916fd07d45a 100644
--- a/samples/client/petstore/R/R/api_response.R
+++ b/samples/client/petstore/R/R/api_response.R
@@ -56,6 +56,9 @@ ApiResponse <- R6::R6Class(
     #' @param to_encoding The target encoding of the return value.
     #' @export
     response_as_text = function(from_encoding = "", to_encoding = "UTF-8") {
+      if (is.null(self$response)) {
+        self$response <- charToRaw(jsonlite::toJSON("NULL"))
+      }
       text_response <- iconv(readBin(self$response, character()), from = from_encoding, to = to_encoding)
       if (is.na(text_response)) {
         warning("The response is binary and will not be converted to text.")