diff --git a/lld/MachO/SymbolTable.cpp b/lld/MachO/SymbolTable.cpp
--- a/lld/MachO/SymbolTable.cpp
+++ b/lld/MachO/SymbolTable.cpp
@@ -64,7 +64,7 @@
   bool wasInserted;
   std::tie(s, wasInserted) = insert(name);
 
-  if (wasInserted)
+  if (wasInserted || isa<Undefined>(s))
     replaceSymbol<DylibSymbol>(s, file, name);
   return s;
 }
diff --git a/lld/test/MachO/resolution.s b/lld/test/MachO/resolution.s
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/resolution.s
@@ -0,0 +1,44 @@
+# REQUIRES: x86
+# RUN: mkdir -p %t
+# RUN: echo '.globl _foo, _bar, _baz; _foo: _bar: _baz:' | \
+# RUN:   llvm-mc -filetype=obj -triple=x86_64-apple-darwin -o %t/libresolution.o
+# RUN: lld -flavor darwinnew -dylib -install_name \
+# RUN:   @executable_path/libresolution.dylib %t/libresolution.o -o %t/libresolution.dylib
+# RUN: lld -flavor darwinnew -dylib -install_name \
+# RUN:   @executable_path/libresolution2.dylib %t/libresolution.o -o %t/libresolution2.dylib
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t/resolution.o
+
+## Check that we select the symbol defined in the first dylib passed on the
+## command line.
+# RUN: lld -flavor darwinnew -o %t/dylib-first -Z -L%t -lresolution -lresolution2 %t/resolution.o
+# RUN: llvm-objdump --macho --bind %t/dylib-first | FileCheck %s --check-prefix=DYLIB-FIRST
+# DYLIB-FIRST:     libresolution _foo
+
+# RUN: lld -flavor darwinnew -o %t/dylib2-first -Z -L%t -lresolution2 -lresolution %t/resolution.o
+# RUN: llvm-objdump --macho --bind %t/dylib2-first | FileCheck %s --check-prefix=DYLIB2-FIRST
+# DYLIB2-FIRST: libresolution2 _foo
+
+## Also check that defined symbols take precedence over dylib symbols.
+# DYLIB-FIRST-NOT: libresolution _bar
+# DYLIB-FIRST-NOT: libresolution _baz
+
+## Check that we pick the dylib symbol over the undefined symbol in the object
+## file, even if the object file appears first on the command line.
+# RUN: lld -flavor darwinnew -o %t/obj-first -Z -L%t %t/resolution.o -lresolution
+# RUN: llvm-objdump --macho --bind %t/obj-first | FileCheck %s --check-prefix=OBJ-FIRST
+# OBJ-FIRST: libresolution _foo
+## But defined symbols should still take precedence.
+# OBJ-FIRST-NOT: libresolution _bar
+# OBJ-FIRST-NOT: libresolution _baz
+
+.globl _main, _bar
+# Global defined symbol
+_bar:
+# Local defined symbol
+_baz:
+
+_main:
+  movq _foo@GOTPCREL(%rip), %rsi
+  movq _bar@GOTPCREL(%rip), %rsi
+  movq _baz@GOTPCREL(%rip), %rsi
+  ret