diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 3342da9192a8..1e54a29c3a9c 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -750,7 +750,9 @@ void OutputSection<ELFT>::relocate(
       Type = R_X86_64_PC32;
       break;
     case SymbolBody::UndefinedKind:
-      continue;
+      assert(Body->isWeak() && "Undefined symbol reached writer");
+      SymVA = 0;
+      break;
     case SymbolBody::LazyKind:
       llvm_unreachable("Lazy symbol reached writer");
     }
diff --git a/lld/test/elf2/relocation-undefined-weak.s b/lld/test/elf2/relocation-undefined-weak.s
new file mode 100644
index 000000000000..db670a78bf6e
--- /dev/null
+++ b/lld/test/elf2/relocation-undefined-weak.s
@@ -0,0 +1,12 @@
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t
+// RUN: lld -flavor gnu2 %t -o %tout
+// RUN: llvm-objdump -d %tout | FileCheck %s
+// REQUIRES: x86
+
+.global _start
+_start:
+  movl $1, sym1(%rip)
+
+.weak sym1
+
+// CHECK: movl    $1, -69642(%rip)