diff --git a/doc/lispref/os.texi b/doc/lispref/os.texi
index 201ca18c1e4..92aaf24b851 100644
--- a/doc/lispref/os.texi
+++ b/doc/lispref/os.texi
@@ -1978,10 +1978,9 @@ The result is @code{nil} if either argument is a NaN.
 
 @defun time-subtract t1 t2
 This returns the time difference @var{t1} @minus{} @var{t2} between
-two time values, normally as a Lisp timestamp but as a float
-if either argument is infinite or a NaN@.
-When the result is a timestamp, it is exact and its clock
+two time values, as a Lisp time value.  The result is exact and its clock
 resolution is no worse than the worse of its two arguments' resolutions.
+The result is floating-point only if it is infinite or a NaN.
 If you need the difference in units
 of elapsed seconds, you can convert it with @code{time-convert} or
 @code{float-time}.  @xref{Time Conversion}.