diff --git a/lldb/include/lldb/Core/cxa_demangle.h b/lldb/include/lldb/Core/cxa_demangle.h
index 66ae8297a5c1..46796b1a33a0 100644
--- a/lldb/include/lldb/Core/cxa_demangle.h
+++ b/lldb/include/lldb/Core/cxa_demangle.h
@@ -10,6 +10,8 @@
 #ifndef _CXA_DEMANGLE_H
 #define _CXA_DEMANGLE_H
 
+// FreeBSD9-STABLE fix (define size_t before including cxxabi.h)
+#include <cstdlib>
 #include <cxxabi.h>
 
 #pragma GCC visibility push(hidden)
diff --git a/lldb/source/Core/Mangled.cpp b/lldb/source/Core/Mangled.cpp
index 7bb58ff24a2f..4852436bb960 100644
--- a/lldb/source/Core/Mangled.cpp
+++ b/lldb/source/Core/Mangled.cpp
@@ -15,6 +15,8 @@
 #if defined(USE_BUILTIN_LIBCXXABI_DEMANGLER)
 #include "lldb/Core/cxa_demangle.h"
 #else
+// FreeBSD9-STABLE requires this to know about size_t in cxxabi.h
+#include <cstddef>
 #include <cxxabi.h>
 #endif