diff --git a/lib/scheme/base.sld b/lib/scheme/base.sld
index f80d5604..65d45262 100644
--- a/lib/scheme/base.sld
+++ b/lib/scheme/base.sld
@@ -35,7 +35,8 @@
    modulo negative?  newline not null?  number->string number?  numerator
    odd?  open-input-bytevector open-input-string open-output-bytevector
    open-output-string or output-port?  pair?  parameterize peek-char
-   peek-u8 port-open?  port?  positive?  procedure?  quasiquote quote
+   peek-u8 input-port-open? output-port-open?  port?  positive?
+   procedure?  quasiquote quote
    quotient raise raise-continuable rational?  rationalize read-bytevector
    read-bytevector!  read-char read-error? read-line read-u8 real?  remainder
    reverse round set!  set-car!  set-cdr!  square string string->list
diff --git a/lib/scheme/extras.scm b/lib/scheme/extras.scm
index 97ec824d..6629c725 100644
--- a/lib/scheme/extras.scm
+++ b/lib/scheme/extras.scm
@@ -61,6 +61,9 @@
 
 (define flush-output-port flush-output)
 
+(define input-port-open? port-open?)
+(define output-port-open? port-open?)
+
 (define (close-port port)
   ((if (input-port? port) close-input-port close-output-port) port))