diff --git a/indra/cwdebug/debug.h b/indra/cwdebug/debug.h
index f127da767..9e832a44c 100644
--- a/indra/cwdebug/debug.h
+++ b/indra/cwdebug/debug.h
@@ -38,15 +38,6 @@
 
 #include <string>
 
-#if LL_WINDOWS
-// On windows, thread-local data is automatically exported.
-#define LL_COMMON_API_TLS __declspec(thread)
-#define CWD_TLS __declspec(thread)
-#else
-#define LL_COMMON_API_TLS LL_COMMON_API __thread
-#define CWD_TLS __thread
-#endif
-
 namespace debug {
 namespace libcwd {
 
diff --git a/indra/llcommon/aithreadid.cpp b/indra/llcommon/aithreadid.cpp
index dfb4a2660..7d179e8e3 100644
--- a/indra/llcommon/aithreadid.cpp
+++ b/indra/llcommon/aithreadid.cpp
@@ -34,8 +34,9 @@
 
 AIThreadID const AIThreadID::sNone(AIThreadID::none);
 apr_os_thread_t AIThreadID::sMainThreadID;
+apr_os_thread_t const undefinedID = (apr_os_thread_t)-1;
 #ifndef LL_DARWIN
-apr_os_thread_t ll_thread_local AIThreadID::lCurrentThread = AIThreadID::undefinedID;
+apr_os_thread_t CWD_TLS AIThreadID::lCurrentThread;
 #endif
 
 void AIThreadID::set_main_thread_id(void)
diff --git a/indra/llcommon/aithreadid.h b/indra/llcommon/aithreadid.h
index c565b5913..9f7893c66 100644
--- a/indra/llcommon/aithreadid.h
+++ b/indra/llcommon/aithreadid.h
@@ -33,28 +33,22 @@
 
 #include <apr_portable.h>	// apr_os_thread_t, apr_os_thread_current(), apr_os_thread_equal().
 #include <iosfwd>			// std::ostream.
-#include "llpreprocessor.h"	// LL_COMMON_API
+#include "llpreprocessor.h"	// LL_COMMON_API, LL_COMMON_API_TLS
 #include "llerror.h"
 
-#if LL_WINDOWS
-#define ll_thread_local __declspec(thread)
-#else
-#define ll_thread_local __thread
-#endif
-
 // Lightweight wrapper around apr_os_thread_t.
 // This class introduces no extra assembly code after optimization; it's only intend is to provide type-safety.
-class LL_COMMON_API AIThreadID
+class AIThreadID
 {
 private:
 	apr_os_thread_t mID;
-	static apr_os_thread_t sMainThreadID;
-	static apr_os_thread_t const undefinedID = (apr_os_thread_t)-1;
+	static LL_COMMON_API apr_os_thread_t sMainThreadID;
+	static LL_COMMON_API apr_os_thread_t const undefinedID;
 #ifndef LL_DARWIN
-	static ll_thread_local apr_os_thread_t lCurrentThread;
+	static LL_COMMON_API_TLS apr_os_thread_t lCurrentThread;
 #endif
 public:
-	static AIThreadID const sNone;
+	static LL_COMMON_API AIThreadID const sNone;
 	enum undefined_thread_t { none };
 	enum dout_print_t { DoutPrint };
 
diff --git a/indra/llcommon/llpreprocessor.h b/indra/llcommon/llpreprocessor.h
index 009871908..be0ec94a3 100644
--- a/indra/llcommon/llpreprocessor.h
+++ b/indra/llcommon/llpreprocessor.h
@@ -195,4 +195,16 @@
 # define LL_COMMON_API
 #endif // LL_COMMON_LINK_SHARED
 
+// Darwin does not support thread-local data.
+#ifndef LL_DARWIN
+#if LL_WINDOWS
+// On windows, thread-local data is automatically exported.
+#define LL_COMMON_API_TLS __declspec(thread)
+#define CWD_TLS __declspec(thread)
+#else // Linux
+#define LL_COMMON_API_TLS LL_COMMON_API __thread
+#define CWD_TLS __thread
+#endif
+#endif
+
 #endif	//	not LL_LINDEN_PREPROCESSOR_H