diff --git a/lib/Target/CBackend/CBackend.cpp b/lib/Target/CBackend/CBackend.cpp
index cbdca3cb5ca..a7c2bd5fc21 100644
--- a/lib/Target/CBackend/CBackend.cpp
+++ b/lib/Target/CBackend/CBackend.cpp
@@ -664,7 +664,7 @@ void CWriter::writeOperand(Value *Operand) {
 static void generateCompilerSpecificCode(std::ostream& Out) {
   // Alloca is hard to get, and we don't want to include stdlib.h here...
   Out << "/* get a declaration for alloca */\n"
-      << "#if defined(sun) || defined(__CYGWIN__)\n"
+      << "#if defined(sun) || defined(__CYGWIN__) || defined(__APPLE__)\n"
       << "extern void *__builtin_alloca(unsigned long);\n"
       << "#define alloca(x) __builtin_alloca(x)\n"
       << "#else\n"
diff --git a/lib/Target/CBackend/Writer.cpp b/lib/Target/CBackend/Writer.cpp
index cbdca3cb5ca..a7c2bd5fc21 100644
--- a/lib/Target/CBackend/Writer.cpp
+++ b/lib/Target/CBackend/Writer.cpp
@@ -664,7 +664,7 @@ void CWriter::writeOperand(Value *Operand) {
 static void generateCompilerSpecificCode(std::ostream& Out) {
   // Alloca is hard to get, and we don't want to include stdlib.h here...
   Out << "/* get a declaration for alloca */\n"
-      << "#if defined(sun) || defined(__CYGWIN__)\n"
+      << "#if defined(sun) || defined(__CYGWIN__) || defined(__APPLE__)\n"
       << "extern void *__builtin_alloca(unsigned long);\n"
       << "#define alloca(x) __builtin_alloca(x)\n"
       << "#else\n"