diff --git a/src/oas/__tests__/__snapshots__/operation.test.ts.snap b/src/oas/__tests__/__snapshots__/operation.test.ts.snap
index 24458fde..97dfad52 100644
--- a/src/oas/__tests__/__snapshots__/operation.test.ts.snap
+++ b/src/oas/__tests__/__snapshots__/operation.test.ts.snap
@@ -787,6 +787,28 @@ Array [
                   ],
                   "type": "string",
                 },
+                "nullableEnumExplicit": Object {
+                  "enum": Array [
+                    null,
+                    "foo",
+                    "bar",
+                  ],
+                  "type": Array [
+                    "string",
+                    "null",
+                  ],
+                },
+                "nullableEnumImplicit": Object {
+                  "enum": Array [
+                    "foo",
+                    "bar",
+                    null,
+                  ],
+                  "type": Array [
+                    "string",
+                    "null",
+                  ],
+                },
                 "photoUrls": Object {
                   "items": Object {
                     "type": "string",
@@ -849,6 +871,28 @@ Array [
                   ],
                   "type": "string",
                 },
+                "nullableEnumExplicit": Object {
+                  "enum": Array [
+                    null,
+                    "foo",
+                    "bar",
+                  ],
+                  "type": Array [
+                    "string",
+                    "null",
+                  ],
+                },
+                "nullableEnumImplicit": Object {
+                  "enum": Array [
+                    "foo",
+                    "bar",
+                    null,
+                  ],
+                  "type": Array [
+                    "string",
+                    "null",
+                  ],
+                },
                 "photoUrls": Object {
                   "items": Object {
                     "type": "string",
@@ -1143,6 +1187,28 @@ Array [
                   ],
                   "type": "string",
                 },
+                "nullableEnumExplicit": Object {
+                  "enum": Array [
+                    null,
+                    "foo",
+                    "bar",
+                  ],
+                  "type": Array [
+                    "string",
+                    "null",
+                  ],
+                },
+                "nullableEnumImplicit": Object {
+                  "enum": Array [
+                    "foo",
+                    "bar",
+                    null,
+                  ],
+                  "type": Array [
+                    "string",
+                    "null",
+                  ],
+                },
                 "photoUrls": Object {
                   "items": Object {
                     "type": "string",
@@ -1205,6 +1271,28 @@ Array [
                   ],
                   "type": "string",
                 },
+                "nullableEnumExplicit": Object {
+                  "enum": Array [
+                    null,
+                    "foo",
+                    "bar",
+                  ],
+                  "type": Array [
+                    "string",
+                    "null",
+                  ],
+                },
+                "nullableEnumImplicit": Object {
+                  "enum": Array [
+                    "foo",
+                    "bar",
+                    null,
+                  ],
+                  "type": Array [
+                    "string",
+                    "null",
+                  ],
+                },
                 "photoUrls": Object {
                   "items": Object {
                     "type": "string",
diff --git a/src/oas/__tests__/fixtures/oas3-kitchen-sink.json b/src/oas/__tests__/fixtures/oas3-kitchen-sink.json
index 26a09ca7..c9d96366 100644
--- a/src/oas/__tests__/fixtures/oas3-kitchen-sink.json
+++ b/src/oas/__tests__/fixtures/oas3-kitchen-sink.json
@@ -312,6 +312,16 @@
             "type": "string",
             "description": "pet status in the store",
             "enum": ["available", "pending", "sold"]
+          },
+          "nullableEnumImplicit": {
+            "type": "string",
+            "nullable": true,
+            "enum": ["foo", "bar"]
+          },
+          "nullableEnumExplicit": {
+            "type": "string",
+            "nullable": true,
+            "enum": [null, "foo", "bar"]
           }
         },
         "required": ["name", "photoUrls"]
diff --git a/src/oas/transformers/schema/keywords/nullable.ts b/src/oas/transformers/schema/keywords/nullable.ts
index 72de6eea..74c4766d 100644
--- a/src/oas/transformers/schema/keywords/nullable.ts
+++ b/src/oas/transformers/schema/keywords/nullable.ts
@@ -26,7 +26,7 @@ const createNullableConverter = (keyword: 'x-nullable' | 'nullable'): Converter
     if (schema[keyword] === true) {
       schema.type = [schema.type, 'null'];
 
-      if (Array.isArray(schema.enum)) {
+      if (Array.isArray(schema.enum) && !schema.enum.includes(null)) {
         schema.enum = [...schema.enum, null];
       }
     } else {