diff --git a/lib/package.json b/lib/package.json
index 1f981cfb..cda240b5 100644
--- a/lib/package.json
+++ b/lib/package.json
@@ -13,7 +13,7 @@
         "openapi-zod-client": "./bin.js"
     },
     "scripts": {
-        "test": "vitest",
+        "test": "export NODE_OPTIONS=$(echo '$NODE_OPTIONS' | sed 's/--openssl-legacy-provider//') vitest",
         "test:ci": "vitest run",
         "lint:ts": "tsc --noEmit",
         "lint": "eslint -c .eslintrc.build.js './src/**/*.ts' --cache --format=pretty",
diff --git a/lib/src/openApiToTypescript.ts b/lib/src/openApiToTypescript.ts
index cb7a09b0..176f2e26 100644
--- a/lib/src/openApiToTypescript.ts
+++ b/lib/src/openApiToTypescript.ts
@@ -47,6 +47,10 @@ const wrapReadOnly =
         return theType;
     };
 
+const handleDefaultValue = (schema: SchemaObject, node: ts.TypeNode | TypeDefinitionObject | string) => {
+    return schema.default !== undefined ? t.union([node, t.reference("undefined")]) : node;
+};
+
 export const getTypescriptFromOpenApi = ({
     schema,
     meta: inheritedMeta,
@@ -79,8 +83,9 @@ TsConversionArgs): ts.Node | TypeDefinitionObject | string => {
                 return t.reference(schemaName);
             }
 
+            let actualSchema: SchemaObject | undefined;
             if (!result) {
-                const actualSchema = ctx.resolver.getSchemaByRef(schema.$ref);
+                actualSchema = ctx.resolver.getSchemaByRef(schema.$ref);
                 if (!actualSchema) {
                     throw new Error(`Schema ${schema.$ref} not found`);
                 }
@@ -93,7 +98,9 @@ TsConversionArgs): ts.Node | TypeDefinitionObject | string => {
                 schemaName = ctx.resolver.resolveRef(schema.$ref)?.normalized;
             }
 
-            return t.reference(schemaName);
+            return actualSchema?.nullable
+                ? t.union([t.reference(schemaName), t.reference("null")])
+                : t.reference(schemaName);
         }
 
         if (Array.isArray(schema.type)) {
@@ -116,7 +123,10 @@ TsConversionArgs): ts.Node | TypeDefinitionObject | string => {
                     }) as TypeDefinition
             );
 
-            return schema.nullable ? t.union([...types, t.reference("null")]) : t.union(types);
+            return handleDefaultValue(
+                schema,
+                schema.nullable ? t.union([...types, t.reference("null")]) : t.union(types)
+            );
         }
 
         if (schema.type === "null") {
@@ -132,7 +142,10 @@ TsConversionArgs): ts.Node | TypeDefinitionObject | string => {
                 (prop) => getTypescriptFromOpenApi({ schema: prop, ctx, meta, options }) as TypeDefinition
             );
 
-            return schema.nullable ? t.union([...types, t.reference("null")]) : t.union(types);
+            return handleDefaultValue(
+                schema,
+                schema.nullable ? t.union([...types, t.reference("null")]) : t.union(types)
+            );
         }
 
         // anyOf = oneOf but with 1 or more = `T extends oneOf ? T | T[] : never`
@@ -147,9 +160,12 @@ TsConversionArgs): ts.Node | TypeDefinitionObject | string => {
                 )
             );
 
-            return schema.nullable
-                ? t.union([oneOf, doWrapReadOnly(t.array(oneOf)), t.reference("null")])
-                : t.union([oneOf, doWrapReadOnly(t.array(oneOf))]);
+            return handleDefaultValue(
+                schema,
+                schema.nullable
+                    ? t.union([oneOf, doWrapReadOnly(t.array(oneOf)), t.reference("null")])
+                    : t.union([oneOf, doWrapReadOnly(t.array(oneOf))])
+            );
         }
 
         if (schema.allOf) {
@@ -177,21 +193,28 @@ TsConversionArgs): ts.Node | TypeDefinitionObject | string => {
                 );
             }
 
-            return schema.nullable ? t.union([t.intersection(types), t.reference("null")]) : t.intersection(types);
+            return handleDefaultValue(
+                schema,
+                schema.nullable ? t.union([t.intersection(types), t.reference("null")]) : t.intersection(types)
+            );
         }
 
         const schemaType = schema.type ? (schema.type.toLowerCase() as NonNullable<typeof schema.type>) : undefined;
         if (schemaType && isPrimitiveType(schemaType)) {
             if (schema.enum) {
                 if (schemaType !== "string" && schema.enum.some((e) => typeof e === "string")) {
-                    return schema.nullable ? t.union([t.never(), t.reference("null")]) : t.never();
+                    return handleDefaultValue(
+                        schema,
+                        schema.nullable ? t.union([t.never(), t.reference("null")]) : t.never()
+                    );
                 }
 
                 const hasNull = schema.enum.includes(null);
                 const withoutNull = schema.enum.filter((f) => f !== null);
-                return schema.nullable || hasNull
-                    ? t.union([...withoutNull, t.reference("null")])
-                    : t.union(withoutNull);
+                return handleDefaultValue(
+                    schema,
+                    schema.nullable || hasNull ? t.union([...withoutNull, t.reference("null")]) : t.union(withoutNull)
+                );
             }
 
             if (schemaType === "string")
@@ -215,19 +238,25 @@ TsConversionArgs): ts.Node | TypeDefinitionObject | string => {
                     arrayOfType = t.reference(arrayOfType);
                 }
 
-                return schema.nullable
-                    ? t.union([doWrapReadOnly(t.array(arrayOfType)), t.reference("null")])
-                    : doWrapReadOnly(t.array(arrayOfType));
+                return handleDefaultValue(
+                    schema,
+                    schema.nullable
+                        ? t.union([doWrapReadOnly(t.array(arrayOfType)), t.reference("null")])
+                        : doWrapReadOnly(t.array(arrayOfType))
+                );
             }
 
-            return schema.nullable
-                ? t.union([doWrapReadOnly(t.array(t.any())), t.reference("null")])
-                : doWrapReadOnly(t.array(t.any()));
+            return handleDefaultValue(
+                schema,
+                schema.nullable
+                    ? t.union([doWrapReadOnly(t.array(t.any())), t.reference("null")])
+                    : doWrapReadOnly(t.array(t.any()))
+            );
         }
 
         if (schemaType === "object" || schema.properties || schema.additionalProperties) {
             if (!schema.properties) {
-                return {};
+                return handleDefaultValue(schema, schema.nullable ? t.union([{}, t.reference("null")]) : {});
             }
 
             canBeWrapped = false;
@@ -283,14 +312,21 @@ TsConversionArgs): ts.Node | TypeDefinitionObject | string => {
                     }
 
                     const isRequired = Boolean(isPartial ? true : schema.required?.includes(prop));
-                    return [`${wrapWithQuotesIfNeeded(prop)}`, isRequired ? propType : t.optional(propType)];
+                    const hasDefault = "default" in propSchema ? propSchema.default !== undefined : false;
+                    return [
+                        `${wrapWithQuotesIfNeeded(prop)}`,
+                        isRequired && !hasDefault ? propType : t.optional(propType),
+                    ];
                 })
             );
 
             const objectType = additionalProperties ? t.intersection([props, additionalProperties]) : props;
 
             if (isInline) {
-                return isPartial ? t.reference("Partial", [doWrapReadOnly(objectType)]) : doWrapReadOnly(objectType);
+                const buffer = isPartial
+                    ? t.reference("Partial", [doWrapReadOnly(objectType)])
+                    : doWrapReadOnly(objectType);
+                return schema.nullable ? t.union([buffer, t.reference("null")]) : buffer;
             }
 
             if (!inheritedMeta?.name) {
@@ -301,7 +337,9 @@ TsConversionArgs): ts.Node | TypeDefinitionObject | string => {
                 return t.type(inheritedMeta.name, doWrapReadOnly(objectType));
             }
 
-            return t.type(inheritedMeta.name, t.reference("Partial", [doWrapReadOnly(objectType)]));
+            return schema.nullable
+                ? t.union([t.type(inheritedMeta.name, doWrapReadOnly(objectType)), t.reference("null")])
+                : t.type(inheritedMeta.name, t.reference("Partial", [doWrapReadOnly(objectType)]));
         }
 
         if (!schemaType) return t.unknown();
diff --git a/lib/src/openApiToZod.ts b/lib/src/openApiToZod.ts
index 2bd35d25..9ec366ae 100644
--- a/lib/src/openApiToZod.ts
+++ b/lib/src/openApiToZod.ts
@@ -89,7 +89,7 @@ export function getZodSchema({ schema: $schema, ctx, meta: inheritedMeta, option
 
         /* when there are multiple allOf we are unable to use a discriminatedUnion as this library adds an
          *   'z.and' to the schema that it creates which breaks type inference */
-        const hasMultipleAllOf = schema.oneOf?.some((obj) => isSchemaObject(obj) && (obj?.allOf || []).length > 1);
+        const hasMultipleAllOf = schema.oneOf?.some((obj) => isSchemaObject(obj) && (obj?.allOf ?? []).length > 1);
         if (schema.discriminator && !hasMultipleAllOf) {
             const propertyName = schema.discriminator.propertyName;
 
@@ -101,7 +101,15 @@ export function getZodSchema({ schema: $schema, ctx, meta: inheritedMeta, option
         }
 
         return code.assign(
-            `z.union([${schema.oneOf.map((prop) => getZodSchema({ schema: prop, ctx, meta, options })).join(", ")}])`
+            `z.union([${schema.oneOf
+                .map(
+                    (prop) =>
+                        getZodSchema({ schema: prop, ctx, meta, options }) +
+                        (isReferenceObject(prop)
+                            ? ""
+                            : getZodChain({ schema: prop, meta: { ...meta, isRequired: true }, options }))
+                )
+                .join(", ")}])`
         );
     }
 
@@ -138,6 +146,7 @@ export function getZodSchema({ schema: $schema, ctx, meta: inheritedMeta, option
             const type = getZodSchema({ schema: schema.allOf[0]!, ctx, meta, options });
             return code.assign(type.toString());
         }
+
         const { patchRequiredSchemaInLoop, noRequiredOnlyAllof, composedRequiredSchema } = inferRequiredSchema(schema);
 
         const types = noRequiredOnlyAllof.map((prop) => {
@@ -146,7 +155,7 @@ export function getZodSchema({ schema: $schema, ctx, meta: inheritedMeta, option
             return zodSchema;
         });
 
-        if (composedRequiredSchema.required.length) {
+        if (composedRequiredSchema.required.length > 0) {
             types.push(
                 getZodSchema({
                     schema: composedRequiredSchema,
@@ -156,6 +165,7 @@ export function getZodSchema({ schema: $schema, ctx, meta: inheritedMeta, option
                 })
             );
         }
+
         const first = types.at(0)!;
         const rest = types
             .slice(1)
@@ -175,8 +185,8 @@ export function getZodSchema({ schema: $schema, ctx, meta: inheritedMeta, option
                     return code.assign(`z.literal(${valueString})`);
                 }
 
-                // eslint-disable-next-line sonarjs/no-nested-template-literals
                 return code.assign(
+                    // eslint-disable-next-line sonarjs/no-nested-template-literals
                     `z.enum([${schema.enum.map((value) => (value === null ? "null" : `"${value}"`)).join(", ")}])`
                 );
             }
diff --git a/lib/tests/enum-null.test.ts b/lib/tests/enum-null.test.ts
index ba377504..4fc81fe9 100644
--- a/lib/tests/enum-null.test.ts
+++ b/lib/tests/enum-null.test.ts
@@ -112,7 +112,7 @@ test("enum-null", async () => {
       import { z } from "zod";
 
       type Compound = Partial<{
-        field: Null1 | Null2 | Null3 | Null4 | string;
+        field: Null1 | Null2 | (Null3 | null) | (Null4 | null) | string;
       }>;
       type Null1 = null;
       type Null2 = "a" | null;
diff --git a/lib/tests/export-all-types.test.ts b/lib/tests/export-all-types.test.ts
index 6169d27f..226c1e8b 100644
--- a/lib/tests/export-all-types.test.ts
+++ b/lib/tests/export-all-types.test.ts
@@ -104,7 +104,7 @@ describe("export-all-types", () => {
         expect(data).toEqual({
             schemas: {
                 Settings: "z.object({ theme_color: z.string(), features: Features.min(1) }).partial().passthrough()",
-                Author: "z.object({ name: z.union([z.string(), z.number()]).nullable(), title: Title.min(1).max(30), id: Id, mail: z.string(), settings: Settings }).partial().passthrough()",
+                Author: "z.object({ name: z.union([z.string().nullable(), z.number()]).nullable(), title: Title.min(1).max(30), id: Id, mail: z.string(), settings: Settings }).partial().passthrough()",
                 Features: "z.array(z.string())",
                 Song: "z.object({ name: z.string(), duration: z.number() }).partial().passthrough()",
                 Playlist:
@@ -207,7 +207,7 @@ describe("export-all-types", () => {
             .passthrough();
           const Author: z.ZodType<Author> = z
             .object({
-              name: z.union([z.string(), z.number()]).nullable(),
+              name: z.union([z.string().nullable(), z.number()]).nullable(),
               title: Title.min(1).max(30),
               id: Id,
               mail: z.string(),
diff --git a/lib/tests/jsdoc.test.ts b/lib/tests/jsdoc.test.ts
index ba91812e..5f30eaa3 100644
--- a/lib/tests/jsdoc.test.ts
+++ b/lib/tests/jsdoc.test.ts
@@ -143,13 +143,13 @@ type ComplexObject = Partial<{
    * @minimum 0
    * @maximum 10
    */
-  manyTagsNum: number;
+  manyTagsNum: number | undefined;
   /**
    * A boolean
    *
    * @default true
    */
-  bool: boolean;
+  bool: boolean | undefined;
   ref: SimpleObject;
   /**
    * An array of SimpleObject