diff --git a/scheme/more-interfaces.scm b/scheme/more-interfaces.scm
index 620c51a..e886b44 100644
--- a/scheme/more-interfaces.scm
+++ b/scheme/more-interfaces.scm
@@ -350,6 +350,7 @@
 	  let-thread-fluids
 	  set-thread-fluid!
 	  make-preserved-thread-fluid
+	  preserve-thread-fluids
 	  fork-thread))
 
 (define-interface search-trees-interface