diff --git a/packages/core/src/patch.ts b/packages/core/src/patch.ts
index 9fa4791a59..7969ae01af 100644
--- a/packages/core/src/patch.ts
+++ b/packages/core/src/patch.ts
@@ -54,19 +54,20 @@ export function parse(patchText: string): Result.Result<ReadonlyArray<Hunk>, Par
   let index = begin + 1
   while (index < end) {
     const line = lines[index]!
-    if (line.startsWith("*** Add File:")) {
-      const path = line.slice("*** Add File:".length).trim()
+    const header = line.trim()
+    if (header.startsWith("*** Add File:")) {
+      const path = header.slice("*** Add File:".length).trim()
       if (!path) {
         index++
         continue
       }
-      const parsed = parseAdd(lines, index + 1)
+      const parsed = parseAdd(lines, index + 1, end)
       hunks.push({ type: "add", path, contents: parsed.content })
       index = parsed.next
       continue
     }
-    if (line.startsWith("*** Delete File:")) {
-      const path = line.slice("*** Delete File:".length).trim()
+    if (header.startsWith("*** Delete File:")) {
+      const path = header.slice("*** Delete File:".length).trim()
       if (!path) {
         index++
         continue
@@ -75,8 +76,8 @@ export function parse(patchText: string): Result.Result<ReadonlyArray<Hunk>, Par
       index++
       continue
     }
-    if (line.startsWith("*** Update File:")) {
-      const path = line.slice("*** Update File:".length).trim()
+    if (header.startsWith("*** Update File:")) {
+      const path = header.slice("*** Update File:".length).trim()
       if (!path) {
         index++
         continue
@@ -87,7 +88,7 @@ export function parse(patchText: string): Result.Result<ReadonlyArray<Hunk>, Par
         movePath = lines[next]!.slice("*** Move to:".length).trim()
         next++
       }
-      const parsed = parseUpdate(lines, next)
+      const parsed = parseUpdate(lines, next, end)
       hunks.push({ type: "update", path, movePath, chunks: parsed.chunks })
       index = parsed.next
       continue
@@ -122,20 +123,20 @@ export function joinBom(text: string, bom: boolean) {
   return bom ? `\uFEFF${stripped}` : stripped
 }
 
-function parseAdd(lines: ReadonlyArray<string>, start: number) {
+function parseAdd(lines: ReadonlyArray<string>, start: number, end: number) {
   const content: string[] = []
   let index = start
-  while (index < lines.length && !lines[index]!.startsWith("***")) {
+  while (index < end && !lines[index]!.startsWith("***")) {
     if (lines[index]!.startsWith("+")) content.push(lines[index]!.slice(1))
     index++
   }
   return { content: content.join("\n"), next: index }
 }
 
-function parseUpdate(lines: ReadonlyArray<string>, start: number) {
+function parseUpdate(lines: ReadonlyArray<string>, start: number, end: number) {
   const chunks: UpdateFileChunk[] = []
   let index = start
-  while (index < lines.length && !lines[index]!.startsWith("***")) {
+  while (index < end && !lines[index]!.startsWith("***")) {
     if (!lines[index]!.startsWith("@@")) {
       index++
       continue
@@ -145,7 +146,7 @@ function parseUpdate(lines: ReadonlyArray<string>, start: number) {
     const newLines: string[] = []
     let endOfFile = false
     index++
-    while (index < lines.length && !lines[index]!.startsWith("@@") && !lines[index]!.startsWith("***")) {
+    while (index < end && !lines[index]!.startsWith("@@") && !lines[index]!.startsWith("***")) {
       const line = lines[index]!
       if (line.startsWith(" ")) {
         oldLines.push(line.slice(1))
diff --git a/packages/core/test/patch.test.ts b/packages/core/test/patch.test.ts
index a39a4d067d..2d872c7f31 100644
--- a/packages/core/test/patch.test.ts
+++ b/packages/core/test/patch.test.ts
@@ -58,6 +58,39 @@ describe("Patch", () => {
     ])
   })
 
+  test("parses a whitespace-padded hunk header", () => {
+    expect(parse("*** Begin Patch\n  *** Update File: foo.txt\n@@\n-old\n+new\n*** End Patch")).toEqual([
+      {
+        type: "update",
+        path: "foo.txt",
+        movePath: undefined,
+        chunks: [{ oldLines: ["old"], newLines: ["new"], changeContext: undefined, endOfFile: undefined }],
+      },
+    ])
+  })
+
+  test("parses leading and trailing whitespace around patch markers", () => {
+    expect(parse(" *** Begin Patch\n*** Update File: file.txt\n@@\n-one\n+two\n*** End Patch ")).toEqual([
+      {
+        type: "update",
+        path: "file.txt",
+        movePath: undefined,
+        chunks: [{ oldLines: ["one"], newLines: ["two"], changeContext: undefined, endOfFile: undefined }],
+      },
+    ])
+  })
+
+  test("parses whitespace on the inner sides of patch marker lines", () => {
+    expect(parse("*** Begin Patch \n*** Update File: file.txt\n@@\n-one\n+two\n *** End Patch")).toEqual([
+      {
+        type: "update",
+        path: "file.txt",
+        movePath: undefined,
+        chunks: [{ oldLines: ["one"], newLines: ["two"], changeContext: undefined, endOfFile: undefined }],
+      },
+    ])
+  })
+
   test("derives fuzzy line updates while preserving BOM", () => {
     const update = Patch.derive("update.txt", [{ oldLines: ["  old   "], newLines: ["new"] }], "\uFEFFold\n")
     expect(update).toEqual({ content: "new\n", bom: true })