diff --git a/sys/src/kern/amd64/syscall.c b/sys/src/kern/amd64/syscall.c
index d55edc3..cc155df 100644
--- a/sys/src/kern/amd64/syscall.c
+++ b/sys/src/kern/amd64/syscall.c
@@ -293,6 +293,7 @@ syscall(Syscalls scallnr, Ureg* ureg)
 		poperror();
 	} else {
 		/* failure: save the error buffer for errstr */
+		retv.l = up->syscallerr;
 		tmp = up->syserrstr;
 		up->syserrstr = up->errstr;
 		up->errstr = tmp;
diff --git a/sys/src/kern/port/portdat.h b/sys/src/kern/port/portdat.h
index 98a2c34..a3ebb85 100644
--- a/sys/src/kern/port/portdat.h
+++ b/sys/src/kern/port/portdat.h
@@ -647,6 +647,7 @@ struct Proc
 	uint8_t		arg[MAXSYSARG*sizeof(void*)];	/* system call arguments */
 	int		nerrlab;
 	Label		errlab[NERR];
+	long		syscallerr;	/* (negative) error code to return from syscalls */
 	char*		syserrstr;	/* last error from a system call, errbuf0 or 1 */
 	char*		errstr;		/* reason we're unwinding the error stack, errbuf1 or 0 */
 	char		errbuf0[ERRMAX];
diff --git a/sys/src/kern/port/portfns.h b/sys/src/kern/port/portfns.h
index b410472..108e8b5 100644
--- a/sys/src/kern/port/portfns.h
+++ b/sys/src/kern/port/portfns.h
@@ -123,7 +123,8 @@ int		encrypt(void*, void*, int);
 void		envcpy(Egrp*, Egrp*);
 int		eqchanddq(Chan*, int, uint32_t, Qid, int);
 int		eqqid(Qid, Qid);
-void		error(char*) __attribute__ ((noreturn));;
+void		error(char*) __attribute__ ((noreturn));
+void		errorl(char*, long) __attribute__ ((noreturn));
 void		errorf(char*, ...);
 void		exhausted(char*);
 void		exit(int) __attribute__ ((noreturn));
diff --git a/sys/src/kern/port/proc.c b/sys/src/kern/port/proc.c
index 046af96..579df01 100644
--- a/sys/src/kern/port/proc.c
+++ b/sys/src/kern/port/proc.c
@@ -1459,15 +1459,21 @@ errorf(char *fmt, ...)
 
 void
 error(char *err)
+{
+	errorl(err, -1);
+}
+
+void
+errorl(char *err, long syscallerr)
 {
 	if(up == nil)
-		panic("error(%s) not in a process", err);
+		panic("errorl(%s, %lld) not in a process", err, syscallerr);
 	spllo();
 
 	if(up->nerrlab >= NERR)
 		panic("error stack too deep");
-	if(err != up->errstr)
-		kstrcpy(up->errstr, err, ERRMAX);
+	up->syscallerr = syscallerr;
+	kstrcpy(up->errstr, err, ERRMAX);
 	setlabel(&up->errlab[NERR-1]);
 	nexterror();
 }