diff --git a/__tests__/load-config-sync.test.ts b/__tests__/load-config-sync.test.ts
index bbf1dd9..48ebbf8 100644
--- a/__tests__/load-config-sync.test.ts
+++ b/__tests__/load-config-sync.test.ts
@@ -376,11 +376,13 @@ describe('loadConfig', () => {
     const variableName = 'VARIABLE_NAME';
     const variableValue = 'The value of this environment variable.';
 
-    it('returns the formatted value.', () => {
+    beforeEach(() => {
       process.env[variableName] = variableValue;
       // @ts-ignore
       fs._setFiles({[filePath]: Buffer.from(fileContent, 'utf8')});
+    });
 
+    it('returns the formatted value.', () => {
       // eslint-disable-next-line unicorn/consistent-function-scoping
       const formatter = (value: string): number => value.length;
 
@@ -399,11 +401,49 @@ describe('loadConfig', () => {
       expect(config.variableProperty).toEqual(formatter(variableValue));
     });
 
-    it('throws if the formatter throws.', () => {
-      process.env[variableName] = variableValue;
-      // @ts-ignore
-      fs._setFiles({[filePath]: Buffer.from(fileContent, 'utf8')});
+    it('returns the formatted value if explicitly required.', () => {
+      // eslint-disable-next-line unicorn/consistent-function-scoping
+      const formatter = (value: string): number => value.length;
+
+      const config = loadConfigSync({
+        fileProperty: {
+          filePath,
+          format: formatter,
+          required: true,
+        },
+        variableProperty: {
+          format: formatter,
+          required: true,
+          variableName,
+        },
+      });
+
+      expect(config.fileProperty).toEqual(formatter(fileContent));
+      expect(config.variableProperty).toEqual(formatter(variableValue));
+    });
+
+    it('returns the formatted value if not required.', () => {
+      // eslint-disable-next-line unicorn/consistent-function-scoping
+      const formatter = (value: string): number => value.length;
+
+      const config = loadConfigSync({
+        fileProperty: {
+          filePath,
+          format: formatter,
+          required: false,
+        },
+        variableProperty: {
+          format: formatter,
+          required: false,
+          variableName,
+        },
+      });
 
+      expect(config.fileProperty).toEqual(formatter(fileContent));
+      expect(config.variableProperty).toEqual(formatter(variableValue));
+    });
+
+    it('throws if the formatter throws.', () => {
       // eslint-disable-next-line unicorn/consistent-function-scoping
       const formatter = (value: string): number => {
         const integer = Number.parseInt(value, 10);
diff --git a/__tests__/load-config.test.ts b/__tests__/load-config.test.ts
index a2c19a2..978ba1f 100644
--- a/__tests__/load-config.test.ts
+++ b/__tests__/load-config.test.ts
@@ -376,11 +376,13 @@ describe('loadConfig', () => {
     const variableName = 'VARIABLE_NAME';
     const variableValue = 'The value of this environment variable.';
 
-    it('returns the formatted value.', async () => {
+    beforeEach(() => {
       process.env[variableName] = variableValue;
       // @ts-ignore
       fs._setFiles({[filePath]: Buffer.from(fileContent, 'utf8')});
+    });
 
+    it('returns the formatted value.', async () => {
       // eslint-disable-next-line unicorn/consistent-function-scoping
       const formatter = (value: string): string => value.toLowerCase();
 
@@ -399,11 +401,49 @@ describe('loadConfig', () => {
       expect(config.variableProperty).toEqual(formatter(variableValue));
     });
 
-    it('rejects if the formatter throws.', async () => {
-      process.env[variableName] = variableValue;
-      // @ts-ignore
-      fs._setFiles({[filePath]: Buffer.from(fileContent, 'utf8')});
+    it('returns the formatted value if explicitly required.', async () => {
+      // eslint-disable-next-line unicorn/consistent-function-scoping
+      const formatter = (value: string): number => value.length;
 
+      const config = await loadConfig({
+        fileProperty: {
+          filePath,
+          format: formatter,
+          required: true,
+        },
+        variableProperty: {
+          format: formatter,
+          required: true,
+          variableName,
+        },
+      });
+
+      expect(config.fileProperty).toEqual(formatter(fileContent));
+      expect(config.variableProperty).toEqual(formatter(variableValue));
+    });
+
+    it('returns the formatted value if not required.', async () => {
+      // eslint-disable-next-line unicorn/consistent-function-scoping
+      const formatter = (value: string): number => value.length;
+
+      const config = await loadConfig({
+        fileProperty: {
+          filePath,
+          format: formatter,
+          required: false,
+        },
+        variableProperty: {
+          format: formatter,
+          required: false,
+          variableName,
+        },
+      });
+
+      expect(config.fileProperty).toEqual(formatter(fileContent));
+      expect(config.variableProperty).toEqual(formatter(variableValue));
+    });
+
+    it('rejects if the formatter throws.', async () => {
       // eslint-disable-next-line unicorn/consistent-function-scoping
       const formatter = (value: string): number => {
         const integer = Number.parseInt(value, 10);
diff --git a/src/format-property.ts b/src/format-property.ts
index cb07f1b..309ccc5 100644
--- a/src/format-property.ts
+++ b/src/format-property.ts
@@ -1,9 +1,4 @@
-import {
-  FormattableConfig,
-  PropertyFormatter,
-  PropertyResult,
-  RequirableConfig,
-} from './types';
+import {BaseConfig, PropertyFormatter, PropertyResult} from './types';
 
 function tryToFormat<Value>(
   value: string,
@@ -18,13 +13,9 @@ function tryToFormat<Value>(
 
 export default function something<Value>(
   propertyResult: PropertyResult<string>,
-  propertyConfig: FormattableConfig<Value> | RequirableConfig,
+  propertyConfig: BaseConfig<Value>,
 ): PropertyResult<string | Value> {
-  const {
-    defaultValue,
-    format,
-    required = true,
-  } = propertyConfig as FormattableConfig<Value>;
+  const {defaultValue, format, required = true} = propertyConfig;
   const hasDefaultValue = typeof defaultValue !== 'undefined';
   const hasError = propertyResult.error !== false;
   const hasFormat = typeof format !== 'undefined';
diff --git a/src/types.ts b/src/types.ts
index d55ccae..32c0b85 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,7 +1,7 @@
 /**
  * Configuration for a property that can be formatted.
  */
-export interface FormattableConfig<Value> {
+export interface BaseConfig<Value> {
   /**
    * The default value of this property.
    */
@@ -16,50 +16,35 @@ export interface FormattableConfig<Value> {
    * Whether this property is required.
    * @defaultValue true
    */
-  required?: true;
+  required?: boolean;
 }
 
 /**
- * Configuration for a property that can be required.
+ * Configuration for a property loaded from an environment variable.
  */
-export interface RequirableConfig {
+export interface EnvironmentConfig<Value> extends BaseConfig<Value> {
   /**
-   * Whether this property is required.
-   * @defaultValue true
+   * The name of the environment variable.
    */
-  required?: boolean;
+  variableName: string;
 }
 
 /**
- * The result loading a property.
- * @internal
+ * Configuration for a property loaded from a secret.
  */
-export interface PropertyResult<Value> {
+export interface FileConfig<Value> extends BaseConfig<Value> {
   /**
-   * The error that was thrown, or false if there is none.
+   * The encoding of the file containing the secret.
+   * @defaultValue 'utf8'
    */
-  error: false | Error;
+  encoding?: BufferEncoding;
 
   /**
-   * The value that was loaded, or undefined if it could not be loaded.
+   * The path to the file containing the secret.
    */
-  value: undefined | Value;
+  filePath: string;
 }
 
-/**
- * Configuration for a property loaded from an environment variable.
- */
-export type EnvironmentConfig<Value> =
-  | (BaseEnvironmentConfig & FormattableConfig<Value>)
-  | (BaseEnvironmentConfig & RequirableConfig);
-
-/**
- * Configuration for a property loaded from a secret.
- */
-export type FileConfig<Value> =
-  | (BaseFileConfig & FormattableConfig<Value>)
-  | (BaseFileConfig & RequirableConfig);
-
 /**
  * The configuration for loading a specific property.
  */
@@ -74,45 +59,35 @@ export type PropertyConfig<Value> =
 export type PropertyFormatter<Value> = (raw: string) => Value;
 
 /**
- * Unwrap a property config to its resultant value.
+ * The result loading a property.
+ * @internal
  */
-export type UnwrapPropertyConfig<
-  PConfig extends PropertyConfig<unknown>
-> = PConfig extends string
-  ? string
-  : PConfig extends {required: false}
-  ? UnwrapResult<PConfig> | void
-  : UnwrapResult<PConfig>;
+export interface PropertyResult<Value> {
+  /**
+   * The error that was thrown, or false if there is none.
+   */
+  error: false | Error;
 
-/**
- * Base configuration for a property loaded from an environment variable.
- */
-interface BaseEnvironmentConfig {
   /**
-   * The name of the environment variable.
+   * The value that was loaded, or undefined if it could not be loaded.
    */
-  variableName: string;
+  value: undefined | Value;
 }
 
 /**
- * Base configuration for a property loaded from a secret.
+ * Unwrap a property config to its resultant value.
  */
-interface BaseFileConfig {
-  /**
-   * The encoding of the file containing the secret.
-   * @defaultValue 'utf8'
-   */
-  encoding?: BufferEncoding;
-
-  /**
-   * The path to the file containing the secret.
-   */
-  filePath: string;
-}
+export type UnwrapPropertyConfig<
+  PConfig extends PropertyConfig<unknown>
+> = PConfig extends string
+  ? string
+  : PConfig extends {required: false}
+  ? UnwrapResult<PConfig> | undefined
+  : UnwrapResult<PConfig>;
 
 /**
  * Unwrap a result to its value.
  */
 type UnwrapResult<
   PConfig extends PropertyConfig<unknown>
-> = PConfig extends FormattableConfig<infer Value> ? Value : string;
+> = PConfig extends BaseConfig<infer Value> ? Value : string;