diff --git a/dom/base/BodyUtil.cpp b/dom/base/BodyUtil.cpp
index 8efac6d223d9..c6bb575a6645 100644
--- a/dom/base/BodyUtil.cpp
+++ b/dom/base/BodyUtil.cpp
@@ -290,6 +290,10 @@ class MOZ_STACK_CLASS FormDataParser {
mFilename.SetIsVoid(true);
mContentType = "text/plain"_ns;
+ while (start != end && NS_IsHTTPWhitespace(*start)) {
+ ++start;
+ }
+
// MUST start with boundary.
if (!PushOverBoundary(boundaryString, start, end)) {
return false;
diff --git a/dom/fetch/tests/mochitest.toml b/dom/fetch/tests/mochitest.toml
index a6031877b966..3f7692d8561a 100644
--- a/dom/fetch/tests/mochitest.toml
+++ b/dom/fetch/tests/mochitest.toml
@@ -1,5 +1,11 @@
[DEFAULT]
+support-files = [
+ "multipart.sjs",
+]
+
["test_ext_response_constructor.html"]
["test_invalid_header_exception.html"]
+
+["test_bug1752761.html"]
diff --git a/dom/fetch/tests/multipart.sjs b/dom/fetch/tests/multipart.sjs
new file mode 100644
index 000000000000..a6a1e5031a75
--- /dev/null
+++ b/dom/fetch/tests/multipart.sjs
@@ -0,0 +1,32 @@
+/* Any copyright is dedicated to the Public Domain.
+ http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+function handleRequest(request, response) {
+ response.seizePower();
+
+ response.write("HTTP/1.1 200 OK\r\n");
+ response.write("Access-Control-Allow-Origin: *\r\n");
+ // See bug 1752761. The extra "\r\n" was the reason why FormDataParser
+ // could not parse this correctly.
+ response.write(
+ "Content-type: multipart/form-data; boundary=boundary\r\n\r\n"
+ );
+ response.write("\r\n");
+ response.write("--boundary\r\n");
+ response.write(
+ 'Content-Disposition: form-data; name="file1"; filename="file1.txt"\r\n'
+ );
+ response.write("Content-Type: text/plain\r\n\r\n");
+ response.write("Content of file1\r\n");
+ response.write("--boundary\r\n");
+ response.write(
+ 'Content-Disposition: form-data; name="file2"; filename="file2.txt"\r\n'
+ );
+ response.write("Content-Type: text/plain\r\n\r\n");
+ response.write("Content of file2\r\n");
+ response.write("--boundary--\r\n");
+ response.write("");
+ response.finish();
+}
diff --git a/dom/fetch/tests/test_bug1752761.html b/dom/fetch/tests/test_bug1752761.html
new file mode 100644
index 000000000000..55bf3e644596
--- /dev/null
+++ b/dom/fetch/tests/test_bug1752761.html
@@ -0,0 +1,27 @@
+
+
+
+
+ Test bug1752761
+
+
+
+
+
+
+
+
+
+