diff --git a/lld/MachO/InputSection.cpp b/lld/MachO/InputSection.cpp
--- a/lld/MachO/InputSection.cpp
+++ b/lld/MachO/InputSection.cpp
@@ -7,12 +7,16 @@
 //===----------------------------------------------------------------------===//
 
 #include "InputSection.h"
+#include "InputFiles.h"
 #include "OutputSegment.h"
 #include "Symbols.h"
 #include "Target.h"
+#include "lld/Common/ErrorHandler.h"
 #include "lld/Common/Memory.h"
 #include "llvm/Support/Endian.h"
+#include "llvm/Support/Path.h"
 
+using namespace llvm;
 using namespace llvm::MachO;
 using namespace llvm::support;
 using namespace lld;
@@ -33,7 +37,10 @@
   for (Reloc &r : relocs) {
     uint64_t va = 0;
     if (auto *s = r.target.dyn_cast<Symbol *>()) {
-      if (auto *dylibSymbol = dyn_cast<DylibSymbol>(s)) {
+      if (isa<Undefined>(s)) {
+        error("undefined symbol " + s->getName() + ", referenced from " +
+              sys::path::filename(file->getName()));
+      } else if (auto *dylibSymbol = dyn_cast<DylibSymbol>(s)) {
         va = target->getDylibSymbolVA(*dylibSymbol, r.type);
       } else {
         va = s->getVA();
diff --git a/lld/test/MachO/invalid/undefined-symbol.s b/lld/test/MachO/invalid/undefined-symbol.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/invalid/undefined-symbol.s
@@ -0,0 +1,11 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o
+# RUN: not lld -flavor darwinnew -Z -o %t %t.o 2>&1 | FileCheck %s -DBASENAME=%basename_t
+# CHECK: error: undefined symbol _foo, referenced from [[BASENAME]]
+
+.globl _main
+.text
+_main:
+  callq _foo
+  movq $0, %rax
+  retq