diff --git a/lld/ELF/LTO.cpp b/lld/ELF/LTO.cpp
--- a/lld/ELF/LTO.cpp
+++ b/lld/ELF/LTO.cpp
@@ -301,7 +301,8 @@
       continue;
     if (linkedBitCodeFiles.contains(f->getName()))
       continue;
-    std::string path = replaceThinLTOSuffix(getThinLTOOutputFile(f->getName()));
+    std::string path =
+        replaceThinLTOSuffix(getThinLTOOutputFile(f->obj->getName()));
     std::unique_ptr<raw_fd_ostream> os = openFile(path + ".thinlto.bc");
     if (!os)
       continue;
diff --git a/lld/test/ELF/lto/thinlto-emit-index-thin-archive.ll b/lld/test/ELF/lto/thinlto-emit-index-thin-archive.ll
new file mode 100644
--- /dev/null
+++ b/lld/test/ELF/lto/thinlto-emit-index-thin-archive.ll
@@ -0,0 +1,49 @@
+; REQUIRES: x86
+
+; RUN: rm -rf %t.dir && mkdir %t.dir && cd %t.dir
+; RUN: mkdir dir1 dir2
+; RUN: llvm-as %s -o ./dir1/main.o
+; RUN: llvm-as %p/Inputs/thinlto.ll -o ./dir1/unused.o
+; RUN: llvm-as %p/Inputs/thin1.ll -o ./dir1/thin.o
+; RUN: llvm-as %p/Inputs/thin2.ll -o ./dir2/thin.o
+; RUN: llvm-ar crT ./dir2/lib.a dir1/unused.o dir1/thin.o dir2/thin.o
+
+;; For a thin archive referencing object files in a different directory,
+;; emit index files (lib.a($member at $offset).thinlto.bc) in the directory
+;; containing the archive, even in the lazy case. The information about the
+;; referenced member's directory is lost.
+; RUN: ld.lld --thinlto-emit-index-files ./dir2/lib.a ./dir1/main.o -o c --save-temps
+; RUN: ls ./dir2 | FileCheck %s --check-prefix CHECK-UNUSED
+
+; CHECK-UNUSED: lib.a(unused.o at {{[1-9][0-9]+}})
+
+;; Index files emitted from object files in a thin archive should have the
+;; offset in the archive specified to avoid collisions
+; RUN: FileCheck %s < c.resolution.txt --check-prefix CHECK-COLLISION
+
+; CHECK-COLLISION: dir1/main.o
+; CHECK-COLLISION: dir2/lib.a(thin.o at {{[1-9][0-9]+}})
+; CHECK-COLLISION-NEXT: -r=./dir2/lib.a(thin.o at {{[1-9][0-9]+}}),blah,pl
+; CHECK-COLLISION: dir2/lib.a(thin.o at {{[1-9][0-9]+}})
+; CHECK-COLLISION-NEXT: -r=./dir2/lib.a(thin.o at {{[1-9][0-9]+}}),foo,pl
+
+;; Clean up
+; RUN: rm -rf ./dir1/*.thinlto.bc
+; RUN: rm -rf ./dir2/*.thinlto.bc
+;; Empty index files for unused files in thin archives should still be emitted
+;; in the same format when using --whole-archive
+; RUN: ld.lld --thinlto-emit-index-files --whole-archive ./dir2/lib.a ./dir1/main.o -o d
+; RUN: ls ./dir2 | FileCheck %s --check-prefix CHECK-UNUSED
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare i32 @blah(i32 %meh)
+declare i32 @foo(i32 %goo)
+
+define void @_start() {
+entry:
+  call i32 @foo(i32 0)
+  call i32 @blah(i32 0)
+  ret void
+}
diff --git a/lld/test/ELF/lto/thinlto-thin-archive-collision.ll b/lld/test/ELF/lto/thinlto-thin-archive-collision.ll
deleted file mode 100644
--- a/lld/test/ELF/lto/thinlto-thin-archive-collision.ll
+++ /dev/null
@@ -1,27 +0,0 @@
-; REQUIRES: x86
-; RUN: rm -fr %t && mkdir %t && cd %t
-; RUN: mkdir thinlto-archives thinlto-archives/a thinlto-archives/b
-; RUN: opt -thinlto-bc -o thinlto-archives/main.o %s
-; RUN: opt -thinlto-bc -o thinlto-archives/a/thin.o %S/Inputs/thin1.ll
-; RUN: opt -thinlto-bc -o thinlto-archives/b/thin.o %S/Inputs/thin2.ll
-; RUN: llvm-ar qcT thinlto-archives/thin.a thinlto-archives/a/thin.o thinlto-archives/b/thin.o
-; RUN: ld.lld thinlto-archives/main.o thinlto-archives/thin.a -o thinlto-archives/main.exe --save-temps
-; RUN: FileCheck %s < thinlto-archives/main.exe.resolution.txt
-
-; CHECK: thinlto-archives/main.o
-; CHECK: thinlto-archives/thin.a(thin.o at {{[1-9][0-9]+}})
-; CHECK-NEXT: -r=thinlto-archives/thin.a(thin.o at {{[1-9][0-9]+}}),foo,pl
-; CHECK: thinlto-archives/thin.a(thin.o at {{[1-9][0-9]+}})
-; CHECK-NEXT: -r=thinlto-archives/thin.a(thin.o at {{[1-9][0-9]+}}),blah,pl
-
-target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
-target triple = "x86_64-scei-ps4"
-
-declare i32 @blah(i32 %meh)
-declare i32 @foo(i32 %goo)
-
-define i32 @_start() {
-  call i32 @foo(i32 0)
-  call i32 @blah(i32 0)
-  ret i32 0
-}