diff --git a/src/lsp/format.lsp b/src/lsp/format.lsp
index 409eb0a0d..cc2955485 100644
--- a/src/lsp/format.lsp
+++ b/src/lsp/format.lsp
@@ -1363,7 +1363,8 @@
     (t
      (let ((spaceleft w))
        (when (and w (or atsign
-                        (minusp number)))
+                        (minusp number)
+                        #+ieee-floating-point (minusp (atan number -1))))
          (decf spaceleft))
        (multiple-value-bind (str len lpoint tpoint)
            (sys::flonum-to-string (abs number) spaceleft d k)
@@ -1389,7 +1390,8 @@
                 t)
                (t
                 (when w (dotimes (i spaceleft) (write-char pad stream)))
-                (if (minusp number)
+                (if (or (minusp number)
+                        #+ieee-floating-point (minusp (atan number -1)))
                     (write-char #\- stream)
                     (if atsign (write-char #\+ stream)))
                 (when lpoint (write-char #\0 stream))