diff --git a/library/x509_crt.c b/library/x509_crt.c
index 4c79a7a..1d81119 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -952,7 +952,7 @@
     return( ret );
 }
 
-#if defined(POLARSSL_THREADING_PTHREAD)
+#if defined(POLARSSL_THREADING_C)
 static threading_mutex_t readdir_mutex = PTHREAD_MUTEX_INITIALIZER;
 #endif
 
@@ -1020,7 +1020,7 @@
     if( dir == NULL)
         return( POLARSSL_ERR_X509_FILE_IO_ERROR );
 
-#if defined(POLARSSL_THREADING_PTHREAD)
+#if defined(POLARSSL_THREADING_C)
     if( ( ret = polarssl_mutex_lock( &readdir_mutex ) ) != 0 )
         return( ret );
 #endif
@@ -1050,7 +1050,7 @@
     closedir( dir );
 
 cleanup:
-#if defined(POLARSSL_THREADING_PTHREAD)
+#if defined(POLARSSL_THREADING_C)
     if( polarssl_mutex_unlock( &readdir_mutex ) != 0 )
         ret = POLARSSL_ERR_THREADING_MUTEX_ERROR;
 #endif