Index: ELF/InputFiles.cpp
===================================================================
--- ELF/InputFiles.cpp
+++ ELF/InputFiles.cpp
@@ -1478,7 +1478,9 @@
     Undefined newSym(&f, name, binding, visibility, type);
     if (canOmitFromDynSym)
       newSym.exportDynamic = false;
-    return symtab->addSymbol(newSym);
+    Symbol *ret = symtab->addSymbol(newSym);
+    ret->referenced = true;
+    return ret;
   }
 
   if (objSym.isCommon())
Index: test/ELF/lto/Inputs/undef.ll
===================================================================
--- /dev/null
+++ test/ELF/lto/Inputs/undef.ll
@@ -0,0 +1,4 @@
+target triple = "x86_64-unknown-linux-gnu"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+declare void @foo()
Index: test/ELF/lto/undef-weak-lazy.ll
===================================================================
--- /dev/null
+++ test/ELF/lto/undef-weak-lazy.ll
@@ -0,0 +1,23 @@
+; REQUIRES: x86
+; RUN: llvm-as %S/Inputs/undef.ll -o %tundef.o
+; RUN: llvm-as %s -o %tweakundef.o
+; RUN: llvm-as %S/Inputs/archive-3.ll -o %tdef.o
+
+;; Test that the lazy bitcode %tdef.o is fetched.
+; RUN: ld.lld %tundef.o --start-lib %tdef.o --end-lib -shared -o %t.so
+; RUN: llvm-nm %t.so | FileCheck %s
+
+;; Test %tweakundef.o does not change STB_GLOBAL to STB_WEAK.
+; RUN: ld.lld %tundef.o %tweakundef.o --start-lib %tdef.o --end-lib -shared -o %t.so
+; RUN: llvm-nm %t.so | FileCheck %s
+
+;; %tweakundef.o does not fetch %tdef.o but %tundef.o does.
+; RUN: ld.lld --start-lib %tdef.o --end-lib %tweakundef.o %tundef.o -shared -o %t.so
+; RUN: llvm-nm %t.so | FileCheck %s
+
+; CHECK: T foo
+
+target triple = "x86_64-unknown-linux-gnu"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+declare extern_weak void @foo()