diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -1992,7 +1992,7 @@
   // Handle -u/--undefined before input files. If both a.a and b.so define foo,
   // -u foo a.a b.so will fetch a.a.
   for (StringRef name : config->undefined)
-    addUnusedUndefined(name);
+    addUnusedUndefined(name)->referenced = true;
 
   // Add all files to the symbol table. This will add almost all
   // symbols that we need to the symbol table. This process might
diff --git a/lld/test/ELF/weak-undef-lib.s b/lld/test/ELF/weak-undef-lib.s
--- a/lld/test/ELF/weak-undef-lib.s
+++ b/lld/test/ELF/weak-undef-lib.s
@@ -17,6 +17,17 @@
 # CHECK-NEXT: Other: 0
 # CHECK-NEXT: Section: Undefined
 
+## -u specifies a STB_DEFAULT undefined symbol, so the definition from %t2.o is
+## fetched.
+# RUN: ld.lld -u foo %t1.o --start-lib %t2.o -o %t1
+# RUN: llvm-readobj --syms %t1 | FileCheck %s --check-prefix=CHECK-U
+
+# CHECK-U:      Name: foo
+# CHECK-U:      Binding:
+# CHECK-U-SAME:          Global
+# CHECK-U:      Section:
+# CHECK-U-SAME:          .text
+
 .weak foo
 call foo@PLT