diff --git a/src/aclocal.m4 b/src/aclocal.m4
index 2184cafc4..a3a249de1 100644
--- a/src/aclocal.m4
+++ b/src/aclocal.m4
@@ -274,9 +274,10 @@ SHAREDPREFIX='lib'
 LIBPREFIX='lib'
 LIBEXT='a'
 PICFLAG='-fPIC'
-THREAD_CFLAGS=''
+THREAD_CFLAGS='-DGC_NO_THREAD_REDIRECTS'
 THREAD_LIBS=''
 THREAD_GC_FLAGS='--enable-threads=posix'
+CFLAGS=''
 INSTALL_TARGET='install'
 THREAD_OBJ="$THREAD_OBJ threads/thread threads/mutex threads/condition_variable threads/semaphore threads/barrier threads/mailbox threads/rwlock"
 clibs='-lm'
@@ -288,7 +289,7 @@ case "${host_os}" in
                 dnl disable floating point exceptions because they
                 dnl lead to segfaults with the android libc
                 with_fpe='no'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
                 ECL_LDRPATH='-Wl,--rpath,~A'
@@ -303,7 +304,7 @@ case "${host_os}" in
         # libdir may have a dollar expression inside
         linux*)
                 thehost='linux'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
@@ -317,7 +318,7 @@ case "${host_os}" in
                 ;;
         gnu*)
                 thehost='gnu'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
@@ -330,7 +331,7 @@ case "${host_os}" in
                 ;;
         kfreebsd*-gnu)
                 thehost='kfreebsd'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
@@ -380,8 +381,6 @@ case "${host_os}" in
                 ;;
         openbsd*)
                 thehost='openbsd'
-                THREAD_CFLAGS=''
-                THREAD_LIBS=''
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
                 ECL_LDRPATH="-Wl,--rpath,~A"
@@ -412,7 +411,7 @@ case "${host_os}" in
                 thehost='cygwin'
                 #enable_threads='no'
                 shared='yes'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
@@ -434,7 +433,7 @@ case "${host_os}" in
                 clibs=''
                 shared='yes'
                 enable_threads='yes'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_GC_FLAGS='--enable-threads=win32'
                 SHARED_LDFLAGS="-Wl,--stack,${ECL_DEFAULT_C_STACK_SIZE}"
                 BUNDLE_LDFLAGS="-Wl,--stack,${ECL_DEFAULT_C_STACK_SIZE}"
@@ -463,7 +462,7 @@ case "${host_os}" in
                 SHARED_LDFLAGS="-dynamiclib ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-bundle ${LDFLAGS}"
                 ECL_LDRPATH='-Wl,-rpath,~A'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                 # The GMP library has not yet been ported to Intel or Arm-OSX
                 case "`uname -m`" in
@@ -501,7 +500,7 @@ case "${host_os}" in
                 thehost='nonstop'
                 shared='yes'
                 PICFLAG='-call_shared'
-                THREAD_CFLAGS='-spthread'
+                THREAD_CFLAGS="-spthread ${THREAD_CFLAGS}"
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
                 ECL_LDRPATH='-Wld=\"-rld_l ~A\"'
@@ -509,7 +508,6 @@ case "${host_os}" in
                 ;;
         haiku*)
                 thehost='haiku'
-                THREAD_LIBS=''
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
                 ECL_LDRPATH="-Wl,--rpath,~A"
@@ -538,7 +536,7 @@ esac
 case "${host}" in
         *-nacl)
                 thehost='linux'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
@@ -550,7 +548,7 @@ case "${host}" in
                 ;;
         *-pnacl)
                 thehost='linux'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                 dnl SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 dnl BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
diff --git a/src/c/mem_bdwgc.d b/src/c/mem_bdwgc.d
index 84acb9cad..bbd62eafb 100644
--- a/src/c/mem_bdwgc.d
+++ b/src/c/mem_bdwgc.d
@@ -1308,6 +1308,24 @@ init_cpu(cl_env_ptr the_env)
   struct GC_stack_base stack;
   GC_get_stack_base(&stack);
   the_env->c_stack.org = (char*)stack.mem_base;
+# ifdef ECL_THREADS
+  if (GC_thread_is_registered() == 0) {
+    GC_register_my_thread(&stack);
+  }
+# endif
+#endif
+  return ECL_NIL;
+}
+
+static cl_object
+free_cpu(cl_env_ptr the_env)
+{
+#ifdef GBC_BOEHM
+# ifdef ECL_THREADS
+  if (GC_thread_is_registered() == 1) {
+    GC_unregister_my_thread();
+  }
+# endif
 #endif
   return ECL_NIL;
 }
@@ -1320,7 +1338,7 @@ static struct ecl_module module_gc = {
   .enable = enable_gc,
   .init_env = ecl_module_no_op_env,
   .init_cpu = init_cpu,
-  .free_cpu = ecl_module_no_op_cpu,
+  .free_cpu = free_cpu,
   .free_env = ecl_module_no_op_env,
   .disable = disable_gc,
   .destroy = ecl_module_no_op
diff --git a/src/c/process.d b/src/c/process.d
index 701fed10a..67eb4761c 100644
--- a/src/c/process.d
+++ b/src/c/process.d
@@ -123,28 +123,6 @@ init_tl_bindings(cl_object process, cl_env_ptr env)
 
 #ifdef ECL_THREADS
 
-static void
-register_gc_thread()
-{
-#ifdef GBC_BOEHM
-  if (GC_thread_is_registered() == 0) {
-    struct GC_stack_base stack;
-    GC_get_stack_base(&stack);
-    GC_register_my_thread(&stack);
-  }
-#endif
-}
-
-static void
-unregister_gc_thread()
-{
-#ifdef GBC_BOEHM
-  if (GC_thread_is_registered() == 1) {
-    GC_unregister_my_thread();
-  }
-#endif
-}
-
 /* Run a process in the current system thread. */
 cl_env_ptr
 ecl_adopt_cpu()
@@ -153,7 +131,6 @@ ecl_adopt_cpu()
   ecl_thread_t current;
   if (the_env != NULL)
     return the_env;
-  register_gc_thread();
   ecl_set_process_self(current);
   the_env = _ecl_alloc_env(0);
   the_env->thread = current;
@@ -177,7 +154,6 @@ ecl_disown_cpu()
 #endif
   ecl_modules_free_env(the_env);
   _ecl_dealloc_env(the_env);
-  unregister_gc_thread();
 }
 
 #ifdef ECL_WINDOWS_THREADS
diff --git a/src/configure b/src/configure
index 1e1c847ba..aded812fa 100755
--- a/src/configure
+++ b/src/configure
@@ -6100,9 +6100,10 @@ SHAREDPREFIX='lib'
 LIBPREFIX='lib'
 LIBEXT='a'
 PICFLAG='-fPIC'
-THREAD_CFLAGS=''
+THREAD_CFLAGS='-DGC_NO_THREAD_REDIRECTS'
 THREAD_LIBS=''
 THREAD_GC_FLAGS='--enable-threads=posix'
+CFLAGS=''
 INSTALL_TARGET='install'
 THREAD_OBJ="$THREAD_OBJ threads/thread threads/mutex threads/condition_variable threads/semaphore threads/barrier threads/mailbox threads/rwlock"
 clibs='-lm'
@@ -6111,8 +6112,8 @@ SONAME_LDFLAGS=''
 case "${host_os}" in
         linux-android*)
                 thehost='ANDROID'
-                                                with_fpe='no'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                with_fpe='no'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
                 ECL_LDRPATH='-Wl,--rpath,~A'
@@ -6131,7 +6132,7 @@ LSP_FEATURES="${LSP_FEATURES} :unix"
         # libdir may have a dollar expression inside
         linux*)
                 thehost='linux'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
@@ -6147,7 +6148,7 @@ LSP_FEATURES="${LSP_FEATURES} :unix"
                 ;;
         gnu*)
                 thehost='gnu'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
@@ -6162,7 +6163,7 @@ LSP_FEATURES="${LSP_FEATURES} :unix"
                 ;;
         kfreebsd*-gnu)
                 thehost='kfreebsd'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
@@ -6228,8 +6229,6 @@ LSP_FEATURES="${LSP_FEATURES} :bsd"
                 ;;
         openbsd*)
                 thehost='openbsd'
-                THREAD_CFLAGS=''
-                THREAD_LIBS=''
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
                 ECL_LDRPATH="-Wl,--rpath,~A"
@@ -6266,7 +6265,7 @@ LSP_FEATURES="${LSP_FEATURES} :unix"
                 thehost='cygwin'
                 #enable_threads='no'
                 shared='yes'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
@@ -6291,7 +6290,7 @@ LSP_FEATURES="${LSP_FEATURES} :unix"
                 clibs=''
                 shared='yes'
                 enable_threads='yes'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_GC_FLAGS='--enable-threads=win32'
                 SHARED_LDFLAGS="-Wl,--stack,${ECL_DEFAULT_C_STACK_SIZE}"
                 BUNDLE_LDFLAGS="-Wl,--stack,${ECL_DEFAULT_C_STACK_SIZE}"
@@ -6433,7 +6432,7 @@ fi
                 SHARED_LDFLAGS="-dynamiclib ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-bundle ${LDFLAGS}"
                 ECL_LDRPATH='-Wl,-rpath,~A'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                 # The GMP library has not yet been ported to Intel or Arm-OSX
                 case "`uname -m`" in
@@ -6477,7 +6476,7 @@ LSP_FEATURES="${LSP_FEATURES} :unix"
                 thehost='nonstop'
                 shared='yes'
                 PICFLAG='-call_shared'
-                THREAD_CFLAGS='-spthread'
+                THREAD_CFLAGS="-spthread ${THREAD_CFLAGS}"
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
                 ECL_LDRPATH='-Wld=\"-rld_l ~A\"'
@@ -6485,7 +6484,6 @@ LSP_FEATURES="${LSP_FEATURES} :unix"
                 ;;
         haiku*)
                 thehost='haiku'
-                THREAD_LIBS=''
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
                 ECL_LDRPATH="-Wl,--rpath,~A"
@@ -6518,7 +6516,7 @@ esac
 case "${host}" in
         *-nacl)
                 thehost='linux'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                 SHARED_LDFLAGS="-shared ${LDFLAGS}"
                 BUNDLE_LDFLAGS="-shared ${LDFLAGS}"
@@ -6532,7 +6530,7 @@ LSP_FEATURES="${LSP_FEATURES} :nacl"
                 ;;
         *-pnacl)
                 thehost='linux'
-                THREAD_CFLAGS='-D_THREAD_SAFE'
+                THREAD_CFLAGS="-D_THREAD_SAFE ${THREAD_CFLAGS}"
                 THREAD_LIBS='-lpthread'
                                                                 CFLAGS="-D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 ${CFLAGS}"
 
@@ -7217,7 +7215,7 @@ if test "${enable_threads}" = "yes" ; then
     as_fn_error $? "Threads aren't supported on this system." "$LINENO" 5
   else
     LIBS="${THREAD_LIBS} ${LIBS}"
-    CFLAGS="${CFLAGS} ${THREAD_CFLAGS}"
+    CFLAGS="${CFLAGS} ${THREAD_CFLAGS} -DGC_NO_THREAD_REDIRECTS"
 
 ac_fn_c_check_func "$LINENO" "pthread_rwlock_init" "ac_cv_func_pthread_rwlock_init"
 if test "x$ac_cv_func_pthread_rwlock_init" = xyes
diff --git a/src/h/ecl.h b/src/h/ecl.h
index 80214bf5a..1fa4363df 100644
--- a/src/h/ecl.h
+++ b/src/h/ecl.h
@@ -63,9 +63,6 @@
 # endif
 # ifdef ECL_THREADS
 #  undef ERROR
-#  ifdef GBC_BOEHM
-#   define CreateThread GC_CreateThread
-#  endif
 # else
 #  error "The Windows ports cannot be built without threads."
 # endif /* ECL_THREADS */