diff --git a/modules/openapi-generator/src/main/resources/r/modelEnum.mustache b/modules/openapi-generator/src/main/resources/r/modelEnum.mustache
index 8471a94cad3c..266cd9f2a872 100644
--- a/modules/openapi-generator/src/main/resources/r/modelEnum.mustache
+++ b/modules/openapi-generator/src/main/resources/r/modelEnum.mustache
@@ -21,11 +21,21 @@
       val <- unlist(local.optional.var)
       enumvec <- .parse_{{name}}()
 
-      stopifnot(length(val) == 1L)
+      if (length(val) == 0L) {
+        val = "DUMMY_ENUM"
+      } else {
+        stopifnot(length(val) == 1L)
+      }
 
-      if (!val %in% enumvec)
+      if (!val %in% enumvec) {
+        if (!(val=="DUMMY_ENUM")) {
           stop("Use one of the valid values: ",
-              paste0(enumvec, collapse = ", "))
+            paste0(enumvec, collapse = ", "))
+        }
+        warning("Initializing {{{classname}}} with DUMMY_ENUM. Use one of the valid values: ",
+          paste0(enumvec, collapse = ", "),
+          ". If you did not manually initialize {{{classname}}}, this may already be overwritten by an enum loaded from a JSON config.")
+      }
       private$value <- val
     },
     #' To JSON string
diff --git a/samples/client/echo_api/r/R/string_enum_ref.R b/samples/client/echo_api/r/R/string_enum_ref.R
index d13f7fbf67aa..ea39a2a6e2c9 100644
--- a/samples/client/echo_api/r/R/string_enum_ref.R
+++ b/samples/client/echo_api/r/R/string_enum_ref.R
@@ -20,11 +20,21 @@ StringEnumRef <- R6::R6Class(
       val <- unlist(local.optional.var)
       enumvec <- .parse_StringEnumRef()
 
-      stopifnot(length(val) == 1L)
+      if (length(val) == 0L) {
+        val = "DUMMY_ENUM"
+      } else {
+        stopifnot(length(val) == 1L)
+      }
 
-      if (!val %in% enumvec)
+      if (!val %in% enumvec) {
+        if (!(val=="DUMMY_ENUM")) {
           stop("Use one of the valid values: ",
-              paste0(enumvec, collapse = ", "))
+            paste0(enumvec, collapse = ", "))
+        }
+        warning("Initializing StringEnumRef with DUMMY_ENUM. Use one of the valid values: ",
+          paste0(enumvec, collapse = ", "),
+          ". If you did not manually initialize StringEnumRef, this may already be overwritten by an enum loaded from a JSON config.")
+      }
       private$value <- val
     },
     #' To JSON string