diff --git a/src/lsp/format.lsp b/src/lsp/format.lsp
index c8a37df7f..f4e710447 100644
--- a/src/lsp/format.lsp
+++ b/src/lsp/format.lsp
@@ -1337,7 +1337,7 @@
       (when (and w (or atsign (minusp number))) (decf spaceleft))
       (multiple-value-bind 
 	  (str len lpoint tpoint)
-	  (sys::flonum-to-string (abs number) spaceleft d k)
+	  (sys::flonum-to-string (abs number) (1- spaceleft) d k)
 	;;if caller specifically requested no fraction digits, suppress the
 	;;optional trailing zero
 	(when (and d (zerop d)) (setq tpoint nil))