diff --git a/package.json b/package.json
index 78e355e..8a9feec 100644
--- a/package.json
+++ b/package.json
@@ -25,7 +25,7 @@
     {
       "path": "pkg/dist-node/index.js",
       "webpack": false,
-      "limit": "3874 B"
+      "limit": "3916 B"
     }
   ],
   "@pika/pack": {
diff --git a/src/internal/source-converters.ts b/src/internal/source-converters.ts
index 652f362..339e030 100644
--- a/src/internal/source-converters.ts
+++ b/src/internal/source-converters.ts
@@ -52,8 +52,11 @@ export const toTuples = (source: Source, recursive = false): TupleSource[] => {
   }
 
   // single tuple like we want to be -> just return it
-  if (isTuple(source) && isFileName(source[0])) {
-    return [source]
+  if (isTuple(source)) {
+    if (isFileName(source[0])) {
+      return [source]
+    }
+    throw new Error(`Source name "${source[0]}" doesn't look like file name`)
   }
 
   // if object source
@@ -61,7 +64,11 @@ export const toTuples = (source: Source, recursive = false): TupleSource[] => {
     const ret: TupleSource[] = []
     for (const key in source) {
       if (source.hasOwnProperty(key)) {
-        ret.push([key, source[key]])
+        if (isFileName(key)) {
+          ret.push([key, source[key]])
+        } else {
+          throw new Error(`Source name "${key}" doesn't look like file name`)
+        }
       }
     }
     return ret
diff --git a/test/manual/test_issue_11.ts b/test/manual/test_issue_11.ts
new file mode 100644
index 0000000..7e5ac8e
--- /dev/null
+++ b/test/manual/test_issue_11.ts
@@ -0,0 +1,16 @@
+import { createWriteStream, readFileSync } from 'fs'
+import { convert, gotenberg, office, pipe, please } from '../../src'
+
+// need to run Gotenberg like this
+// docker run --rm -p 3500:3000 thecodingmachine/gotenberg:6
+
+const buffer = readFileSync('document.docx')
+
+pipe(
+  gotenberg('http://localhost:3500'),
+  convert,
+  office,
+  please
+)(['aaaa', buffer])
+  .then(pdf => pdf.pipe(createWriteStream(`${__dirname}/document.pdf`)))
+  .catch(console.error)
diff --git a/test/please.spec.ts b/test/please.spec.ts
index bdb5f8b..b427cad 100644
--- a/test/please.spec.ts
+++ b/test/please.spec.ts
@@ -118,3 +118,40 @@ test('Should throw on wrong source filenames', () => {
       `looks like you didn't set filename for document`
   )
 })
+
+test('Should throw on wrong source filename 2', () => {
+  const request1: OfficeRequest = {
+    type: RequestType.Office,
+    source: ['aaaaa', 'test'],
+  } as any
+
+  expect(() => please(request1)).toThrow(`Source name "aaaaa" doesn't look like file name`)
+
+  const request2: OfficeRequest = {
+    type: RequestType.Office,
+    source: { aaaaa: 'test' },
+  } as any
+
+  expect(() => please(request2)).toThrow(`Source name "aaaaa" doesn't look like file name`)
+
+  const request3: OfficeRequest = {
+    type: RequestType.Office,
+    source: [['aaaaa', 'test']],
+  } as any
+
+  expect(() => please(request3)).toThrow(`Source name "aaaaa" doesn't look like file name`)
+
+  const request4: OfficeRequest = {
+    type: RequestType.Office,
+    source: [{ aaaaa: 'test' }],
+  } as any
+
+  expect(() => please(request4)).toThrow(`Source name "aaaaa" doesn't look like file name`)
+
+  const request5: OfficeRequest = {
+    type: RequestType.Office,
+    source: [['aaaaa', 'test'], { aaaaa: 'test' }],
+  } as any
+
+  expect(() => please(request5)).toThrow(`Source name "aaaaa" doesn't look like file name`)
+})