diff --git a/doc/ref/api-io.texi b/doc/ref/api-io.texi
index 52dfdd4fe..6a50424a4 100644
--- a/doc/ref/api-io.texi
+++ b/doc/ref/api-io.texi
@@ -949,9 +949,8 @@ used only during port creation are not retained.
 
 @deffn {Scheme Procedure} port-filename port
 @deffnx {C Function} scm_port_filename (port)
-Return the filename associated with @var{port}.  This function returns
-the strings "standard input", "standard output" and "standard error"
-when called on the current input, output and error ports respectively.
+Return the filename associated with @var{port}, or @code{#f} if no
+filename is associated with the port.
 
 @var{port} must be open, @code{port-filename} cannot be used once the
 port is closed.
diff --git a/libguile/ports.c b/libguile/ports.c
index 6a51ddc3c..a48cc8607 100644
--- a/libguile/ports.c
+++ b/libguile/ports.c
@@ -1942,9 +1942,8 @@ SCM_DEFINE (scm_set_port_column_x, "set-port-column!", 2, 0, 0,
 
 SCM_DEFINE (scm_port_filename, "port-filename", 1, 0, 0,
             (SCM port),
-	    "Return the filename associated with @var{port}.  This function returns\n"
-	    "the strings \"standard input\", \"standard output\" and \"standard error\"\n"
-	    "when called on the current input, output and error ports respectively.")
+	    "Return the filename associated with @var{port}, or @code{#f}\n"
+	    "if no filename is associated with the port.")
 #define FUNC_NAME s_scm_port_filename
 {
   port = SCM_COERCE_OUTPORT (port);