diff --git a/libs/fst/config.h b/libs/fst/config.h
index 0598fb8c5..cd036f16a 100644
--- a/libs/fst/config.h
+++ b/libs/fst/config.h
@@ -21,6 +21,9 @@
 #undef HAVE_LIBPTHREAD
 #undef HAVE_FSEEKO
 #endif
+#ifdef __FreeBSD__
+#undef HAVE_ALLOCA_H
+#endif
 
 # ifndef __STDC_FORMAT_MACROS
 #  define __STDC_FORMAT_MACROS 1