diff --git a/lib/chibi/time.module b/lib/chibi/time.module
index 3bf62fa6..bdf219cc 100644
--- a/lib/chibi/time.module
+++ b/lib/chibi/time.module
@@ -2,7 +2,7 @@
 (module (chibi time)
   (export current-seconds get-time-of-day set-time-of-day!
           seconds->time seconds->string time->seconds time->string
-          timeval-seconds timeval-microseconds
+          make-timeval timeval-seconds timeval-microseconds
           timezone-offset timezone-dst-time
           time-second time-minute time-hour time-day time-month time-year
           time-day-of-week time-day-of-year time-dst?
diff --git a/lib/chibi/time.stub b/lib/chibi/time.stub
index 88a192c9..7746ee6c 100644
--- a/lib/chibi/time.stub
+++ b/lib/chibi/time.stub
@@ -19,6 +19,7 @@
 
 (define-c-struct timeval
   predicate: timeval?
+  constructor: (make-timeval tv_sec tv_usec)
   (time_t  tv_sec          timeval-seconds)
   (int     tv_usec         timeval-microseconds))
 
diff --git a/lib/srfi/18.module b/lib/srfi/18.module
index eabe8b8c..031c1477 100644
--- a/lib/srfi/18.module
+++ b/lib/srfi/18.module
@@ -15,7 +15,8 @@
    join-timeout-exception? abandoned-mutex-exception?
    terminated-thread-exception? uncaught-exception?
    uncaught-exception-reason)
-  (import (scheme) (srfi 9) (chibi ast) (chibi time))
+  (import (scheme) (srfi 9) (chibi ast)
+          (except (chibi time) time->seconds seconds->time))
   (include "18/types.scm")
   (include-shared "18/threads")
   (include "18/interface.scm"))
diff --git a/lib/srfi/18/interface.scm b/lib/srfi/18/interface.scm
index dd1a46dc..84041576 100644
--- a/lib/srfi/18/interface.scm
+++ b/lib/srfi/18/interface.scm
@@ -40,6 +40,12 @@
 (define current-time get-time-of-day)
 (define time? timeval?)
 
+(define (time->seconds x)
+  (timeval-seconds (if (pair? x) (car x) x)))
+
+(define (seconds->time x)
+  (make-timeval (if (inexact? x) (inexact->exact x) x) 0))
+
 (define (join-timeout-exception? x)
   (and (exception? x)
        (equal? (exception-message x) "timed out waiting for thread")))