diff --git a/src/tests/webR/webr-main.test.ts b/src/tests/webR/webr-main.test.ts
index 5e737208..8e22d3f7 100644
--- a/src/tests/webR/webr-main.test.ts
+++ b/src/tests/webR/webr-main.test.ts
@@ -111,9 +111,9 @@ describe('Evaluate R code', () => {
 
   test('Error conditions are re-thrown in JS when executing an R function', async () => {
     const fn = await webR.evalR('sin') as RFunction;
-    let throws = fn("abc");
+    let throws = fn('abc');
     await expect(throws).rejects.toThrow('non-numeric argument to mathematical function');
-    throws = fn.exec("abc");
+    throws = fn.exec('abc');
     await expect(throws).rejects.toThrow('non-numeric argument to mathematical function');
   });
 
@@ -166,18 +166,19 @@ describe('Evaluate R code', () => {
       captureConditions: true,
     });
 
-    let outType = await result.output.pluck(1, 'type')!;
-    let outData = await result.output.pluck(1, 'data')!;
+    let outType = await result.output.pluck(1, 'type') as RCharacter;
+    let outData = await result.output.pluck(1, 'data') as RCharacter;
+
     expect(await outType.toString()).toEqual('stdout');
     expect(await outData.toString()).toContain('Hello, stdout!');
 
-    outType = await result.output.pluck(2, 'type')!;
-    outData = await result.output.pluck(2, 'data', 'message')!;
+    outType = await result.output.pluck(2, 'type') as RCharacter;
+    outData = await result.output.pluck(2, 'data', 'message') as RCharacter;
     expect(await outType.toString()).toEqual('message');
     expect(await outData.toString()).toContain('Hello, message!');
 
-    outType = await result.output.pluck(3, 'type')!;
-    outData = await result.output.pluck(3, 'data', 'message')!;
+    outType = await result.output.pluck(3, 'type') as RCharacter;
+    outData = await result.output.pluck(3, 'data', 'message') as RCharacter;
     expect(await outType.toString()).toEqual('warning');
     expect(await outData.toString()).toContain('Hello, warning!');
 
diff --git a/src/webR/proxy.ts b/src/webR/proxy.ts
index cbd9ab99..06787d68 100644
--- a/src/webR/proxy.ts
+++ b/src/webR/proxy.ts
@@ -43,15 +43,19 @@ export type DistProxy<U> = U extends RWorker.RObject ? RProxy<U> : U;
  * converted to a corresponding type using `RProxify` recursively.
  * @typeParam T The type to convert.
  */
-export type RProxify<T> = T extends Array<any>
+export type RProxify<T> = T extends Array<any> // [RObject, RObject, ...]
   ? Promise<DistProxy<T[0]>[]>
-  : T extends (...args: infer U) => any
+  : T extends (...args: infer U) => any // (...args) => <RObject>
   ? (
       ...args: {
         [V in keyof U]: DistProxy<U[V]>;
       }
     ) => RProxify<ReturnType<T>>
-  : Promise<DistProxy<T>>;
+  : T extends { result: RWorker.RObject, output: RWorker.RObject } // Return type of .capture()
+  ? Promise<{
+      [U in keyof T]: DistProxy<T[U]>
+    }>
+  : Promise<DistProxy<T>>; // RObject, any other types
 
 /**
  * Create an {@link RProxy} based on an {@link RWorker.RObject} type parameter.
diff --git a/src/webR/webr-main.ts b/src/webR/webr-main.ts
index 392f0603..e547d27c 100644
--- a/src/webR/webr-main.ts
+++ b/src/webR/webr-main.ts
@@ -599,17 +599,21 @@ export class Shelter {
   /**
    * Evaluate the given R code, capturing output.
    *
-   * Stream outputs and conditions raised during exectution are captured and
+   * Stream outputs and conditions raised during execution are captured and
    * returned as part of the output of this function. Returned R objects are
    * protected by the shelter.
    * @param {string} code The R code to evaluate.
    * @param {EvalROptions} [options] Options for the execution environment.
-   * @returns {Promise<{result: RObject, output: unknown[]}>} An object
-   * containing the result of the computation and and array of captured output.
+   * @returns {Promise<{
+   *   result: RObject,
+   *   output: { type: string; data: any }[],
+   *   images: ImageBitmap[]
+   * }>} An object containing the result of the computation, an array of output,
+   *   and an array of captured plots.
    */
   async captureR(code: string, options: EvalROptions = {}): Promise<{
     result: RObject;
-    output: unknown[];
+    output: { type: string; data: any }[];
     images: ImageBitmap[];
   }> {
     const opts = replaceInObject(options, isRObject, (obj: RObject) => obj._payload);