diff --git a/code/math/implementation.lisp b/code/math/implementation.lisp
index a5715dca..97e20288 100644
--- a/code/math/implementation.lisp
+++ b/code/math/implementation.lisp
@@ -24,17 +24,17 @@
 (defun round-to-odd/32 (g cp)
   (let ((p (* g cp)))
     (logior (ldb (byte 32 64) p)
-            (if (> (ldb (byte 32 32) p) 1) 1 0))))
+            (if (> p #x1FFFFFFFF) 1 0))))
 
 (defun round-to-odd/64 (g cp)
   (let ((p (* g cp)))
     (logior (ldb (byte 64 128) p)
-            (if (> (ldb (byte 64 64) p) 1) 1 0))))
+            (if (> p #x1FFFFFFFFFFFFFFFF) 1 0))))
 
 (defun round-to-odd/128 (g cp)
   (let ((p (* g cp)))
     (logior (ldb (byte 128 256) p)
-            (if (> (ldb (byte 128 128) p) 1) 1 0))))
+            (if (> p #x1FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF) 1 0))))
 
 (defconstant +expt10/min-exponent/32+ -31)