diff --git a/types/stream-buffers/index.d.ts b/types/stream-buffers/index.d.ts
index aa0602b835..59cf0e1df1 100644
--- a/types/stream-buffers/index.d.ts
+++ b/types/stream-buffers/index.d.ts
@@ -15,7 +15,7 @@ export class WritableStreamBuffer extends stream.Writable {
     constructor(options?: WritableStreamBufferOptions);
     size(): number;
     maxSize(): number;
-    getContents(length?: number): any;
+    getContents(length?: number): Buffer;
     getContentsAsString(encoding?: string, length?: number): string;
 }
 
diff --git a/types/stream-buffers/stream-buffers-tests.ts b/types/stream-buffers/stream-buffers-tests.ts
index c7051023b8..b50a1db286 100644
--- a/types/stream-buffers/stream-buffers-tests.ts
+++ b/types/stream-buffers/stream-buffers-tests.ts
@@ -20,16 +20,16 @@ myWritableStreamBuffer.size();
 myWritableStreamBuffer.maxSize();
 
 // Gets all held data as a Buffer.
-myWritableStreamBuffer.getContents();
+const contents: Buffer = myWritableStreamBuffer.getContents();
 
 // Gets all held data as a utf8 string.
-myWritableStreamBuffer.getContentsAsString('utf8');
+const stringContents: string = myWritableStreamBuffer.getContentsAsString('utf8');
 
 // Gets first 5 bytes as a Buffer.
-myWritableStreamBuffer.getContents(5);
+const contents2: Buffer = myWritableStreamBuffer.getContents(5);
 
 // Gets first 5 bytes as a utf8 string.
-myWritableStreamBuffer.getContentsAsString('utf8', 5);
+const stringContents2: string = myWritableStreamBuffer.getContentsAsString('utf8', 5);
 
 const myReadableStreamBuffer = new streamBuffers.ReadableStreamBuffer({
     frequency: 10,   // in milliseconds.