diff --git a/lld/MachO/Driver.cpp b/lld/MachO/Driver.cpp
--- a/lld/MachO/Driver.cpp
+++ b/lld/MachO/Driver.cpp
@@ -1138,10 +1138,6 @@
     if (!orderFile.empty())
       parseOrderFile(orderFile);
 
-    if (config->outputType == MH_EXECUTE && isa<Undefined>(config->entry)) {
-      error("undefined symbol: " + toString(*config->entry));
-      return false;
-    }
     // FIXME: This prints symbols that are undefined both in input files and
     // via -u flag twice.
     for (const Symbol *undefined : config->explicitUndefineds) {
diff --git a/lld/MachO/Writer.cpp b/lld/MachO/Writer.cpp
--- a/lld/MachO/Writer.cpp
+++ b/lld/MachO/Writer.cpp
@@ -1049,8 +1049,14 @@
 }
 
 template <class LP> void Writer::run() {
-  if (config->entry)
-    prepareBranchTarget(config->entry);
+  if (config->entry) {
+    if (auto *undefined = dyn_cast<Undefined>(config->entry))
+      treatUndefinedSymbol(*undefined);
+    // treatUndefinedSymbol() can replace sym with a DylibSymbol; re-check.
+    if (!isa<Undefined>(config->entry))
+      prepareBranchTarget(config->entry);
+  }
+
   scanRelocations();
   if (in.stubHelper->isNeeded())
     in.stubHelper->setup();
diff --git a/lld/test/MachO/entry-symbol.s b/lld/test/MachO/entry-symbol.s
--- a/lld/test/MachO/entry-symbol.s
+++ b/lld/test/MachO/entry-symbol.s
@@ -22,7 +22,11 @@
 # CHECK-NEXT: entryoff [[#ENTRYOFF]]
 
 # RUN: %lld -lSystem -o %t/dysym-main %t/not-main.o %t/libfoo.dylib -e _dysym_main
-# RUN: llvm-objdump --macho --all-headers --indirect-symbols --lazy-bind %t/dysym-main | FileCheck %s --check-prefix=DYSYM
+# RUN: llvm-objdump --macho --all-headers --indirect-symbols --lazy-bind %t/dysym-main | FileCheck %s --check-prefix=DYSYM -DDYLIB=libfoo
+
+# RUN: %lld -lSystem -o %t/dyn-lookup %t/not-main.o -e _dysym_main -undefined dynamic_lookup
+# RUN: llvm-objdump --macho --all-headers --indirect-symbols --lazy-bind %t/dyn-lookup | FileCheck %s --check-prefix=DYSYM -DDYLIB=flat-namespace
+
 # DYSYM-LABEL: Indirect symbols for (__TEXT,__stubs) 1 entries
 # DYSYM-NEXT:  address                      index  name
 # DYSYM-NEXT:  0x[[#%x,DYSYM_ENTRY_ADDR:]]  [[#]]  _dysym_main
@@ -30,8 +34,8 @@
 # DYSYM-NEXT:  cmdsize  24
 # DYSYM-NEXT:  entryoff [[#%u, DYSYM_ENTRY_ADDR - 0x100000000]]
 # DYSYM-LABEL: Lazy bind table:
-# DYSYM-NEXT:  segment  section            address     dylib            symbol
-# DYSYM-NEXT:  __DATA   __la_symbol_ptr    {{.*}}      libfoo       _dysym_main
+# DYSYM-NEXT:  segment  section            address     dylib        symbol
+# DYSYM-NEXT:  __DATA   __la_symbol_ptr    {{.*}}      [[DYLIB]]    _dysym_main
 
 # RUN: %lld -lSystem -o %t/weak-dysym-main %t/not-main.o %t/libfoo.dylib -e _weak_dysym_main
 # RUN: llvm-objdump --macho --all-headers --indirect-symbols --bind --weak-bind %t/weak-dysym-main | FileCheck %s --check-prefix=WEAK-DYSYM
@@ -42,8 +46,8 @@
 # WEAK-DYSYM-NEXT:  cmdsize  24
 # WEAK-DYSYM-NEXT:  entryoff [[#%u, DYSYM_ENTRY_ADDR - 0x100000000]]
 # WEAK-DYSYM-LABEL: Bind table:
-# WEAK-DYSYM-NEXT:  segment  section          address  type     addend  dylib      symbol
-# WEAK-DYSYM:       __DATA   __la_symbol_ptr  {{.*}}   pointer       0  libfoo _weak_dysym_main
+# WEAK-DYSYM-NEXT:  segment  section          address  type     addend  dylib   symbol
+# WEAK-DYSYM:       __DATA   __la_symbol_ptr  {{.*}}   pointer       0  libfoo  _weak_dysym_main
 # WEAK-DYSYM-LABEL: Weak bind table:
 # WEAK-DYSYM-NEXT:  segment  section          address  type     addend  symbol
 # WEAK-DYSYM-NEXT:  __DATA   __la_symbol_ptr  {{.*}}   pointer       0  _weak_dysym_main