diff --git a/stl/inc/xthreads.h b/stl/inc/xthreads.h
index 7f78cec33f..a34afd85e4 100644
--- a/stl/inc/xthreads.h
+++ b/stl/inc/xthreads.h
@@ -96,10 +96,6 @@ enum { // mutex types
     _Mtx_recursive = 0x100
 };
 
-#ifdef _CRTBLD
-_CRTIMP2_PURE _Thrd_result __cdecl _Mtx_init(_Mtx_t*, int);
-_CRTIMP2_PURE void __cdecl _Mtx_destroy(_Mtx_t);
-#endif // _CRTBLD
 _CRTIMP2_PURE void __cdecl _Mtx_init_in_situ(_Mtx_t, int);
 _CRTIMP2_PURE void __cdecl _Mtx_destroy_in_situ(_Mtx_t);
 _CRTIMP2_PURE int __cdecl _Mtx_current_owns(_Mtx_t);
@@ -117,10 +113,6 @@ void __cdecl _Smtx_unlock_exclusive(_Smtx_t*);
 void __cdecl _Smtx_unlock_shared(_Smtx_t*);
 
 // condition variables
-#ifdef _CRTBLD
-_CRTIMP2_PURE _Thrd_result __cdecl _Cnd_init(_Cnd_t*);
-_CRTIMP2_PURE void __cdecl _Cnd_destroy(_Cnd_t);
-#endif // _CRTBLD
 _CRTIMP2_PURE void __cdecl _Cnd_init_in_situ(_Cnd_t);
 _CRTIMP2_PURE void __cdecl _Cnd_destroy_in_situ(_Cnd_t);
 _CRTIMP2_PURE _Thrd_result __cdecl _Cnd_wait(_Cnd_t, _Mtx_t); // TRANSITION, ABI: Always succeeds
diff --git a/stl/src/cond.cpp b/stl/src/cond.cpp
index fa094b0440..ea61d15575 100644
--- a/stl/src/cond.cpp
+++ b/stl/src/cond.cpp
@@ -28,6 +28,7 @@ _CRTIMP2_PURE void __cdecl _Cnd_init_in_situ(const _Cnd_t cond) { // initialize
 
 _CRTIMP2_PURE void __cdecl _Cnd_destroy_in_situ(_Cnd_t) {} // destroy condition variable in situ
 
+// TRANSITION, ABI: used only by _Thrd_create(), which is preserved for binary compatibility
 _CRTIMP2_PURE _Thrd_result __cdecl _Cnd_init(_Cnd_t* const pcond) { // initialize
     *pcond = nullptr;
 
@@ -41,6 +42,7 @@ _CRTIMP2_PURE _Thrd_result __cdecl _Cnd_init(_Cnd_t* const pcond) { // initializ
     return _Thrd_result::_Success;
 }
 
+// TRANSITION, ABI: used only by _Thrd_create(), which is preserved for binary compatibility
 _CRTIMP2_PURE void __cdecl _Cnd_destroy(const _Cnd_t cond) { // clean up
     if (cond) { // something to do, do it
         _Cnd_destroy_in_situ(cond);
diff --git a/stl/src/cthread.cpp b/stl/src/cthread.cpp
index 618037bbfd..2fb7df1301 100644
--- a/stl/src/cthread.cpp
+++ b/stl/src/cthread.cpp
@@ -109,6 +109,12 @@ _CRTIMP2_PURE unsigned int __cdecl _Thrd_hardware_concurrency() { // return numb
     return info.dwNumberOfProcessors;
 }
 
+// TRANSITION, ABI: these functions are used only by _Thrd_create()
+_CRTIMP2_PURE _Thrd_result __cdecl _Mtx_init(_Mtx_t*, int);
+_CRTIMP2_PURE void __cdecl _Mtx_destroy(_Mtx_t);
+_CRTIMP2_PURE _Thrd_result __cdecl _Cnd_init(_Cnd_t*);
+_CRTIMP2_PURE void __cdecl _Cnd_destroy(_Cnd_t);
+
 // TRANSITION, ABI: _Thrd_create() is preserved for binary compatibility
 _CRTIMP2_PURE _Thrd_result __cdecl _Thrd_create(_Thrd_t* thr, _Thrd_start_t func, void* d) { // create thread
     _Thrd_result res;
diff --git a/stl/src/mutex.cpp b/stl/src/mutex.cpp
index 98cf98d1cd..1aeb9e038d 100644
--- a/stl/src/mutex.cpp
+++ b/stl/src/mutex.cpp
@@ -50,6 +50,7 @@ _CRTIMP2_PURE void __cdecl _Mtx_destroy_in_situ(_Mtx_t mtx) { // destroy mutex i
     (void) mtx;
 }
 
+// TRANSITION, ABI: used only by _Thrd_create(), which is preserved for binary compatibility
 _CRTIMP2_PURE _Thrd_result __cdecl _Mtx_init(_Mtx_t* mtx, int type) { // initialize mutex
     *mtx = nullptr;
 
@@ -65,6 +66,7 @@ _CRTIMP2_PURE _Thrd_result __cdecl _Mtx_init(_Mtx_t* mtx, int type) { // initial
     return _Thrd_result::_Success;
 }
 
+// TRANSITION, ABI: used only by _Thrd_create(), which is preserved for binary compatibility
 _CRTIMP2_PURE void __cdecl _Mtx_destroy(_Mtx_t mtx) { // destroy mutex
     if (mtx) { // something to do, do it
         _Mtx_destroy_in_situ(mtx);