diff --git a/CHANGES b/CHANGES
index 78a4058..35e2225 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,5 +1,6 @@
 0.27:
   add fmt_strm
+  add iob_addbuf_munmap
 
 0.26:
   fix really pathological case where io_timeouted would never
diff --git a/io/iob_addbuf_munmap.c b/io/iob_addbuf_munmap.c
new file mode 100644
index 0000000..bd8f3c5
--- /dev/null
+++ b/io/iob_addbuf_munmap.c
@@ -0,0 +1,5 @@
+#include "iob_internal.h"
+
+int iob_addbuf_free(io_batch* b,const void* buf,uint64 n) {
+  return iob_addbuf_internal(b,buf,n,2);
+}
diff --git a/io/iob_reset.c b/io/iob_reset.c
index 2f99424..027a3b0 100644
--- a/io/iob_reset.c
+++ b/io/iob_reset.c
@@ -1,4 +1,5 @@
 #include <stdlib.h>
+#include <sys/mman.h>
 #include "byte.h"
 #include "iob_internal.h"
 
@@ -7,10 +8,18 @@ void iob_reset(io_batch* b) {
   iob_entry* x=array_start(&b->b);
   l=array_length(&b->b,sizeof(iob_entry));
   for (i=0; i<l; ++i) {
-    if (x[i].type==FROMBUF_FREE)
+    switch (x[i].type) {
+    case FROMBUF_FREE:
       free((char*)x[i].buf);
-    if (x[i].type==FROMFILE_CLOSE)
+      break;
+    case FROMBUF_MUNMAP:
+      munmap((char*)x[i].buf,x[i].n);
+      break;
+    case FROMFILE_CLOSE:
       io_close(x[i].fd);
+    default:
+      break;
+    }
   }
   array_reset(&b->b);
   byte_zero(b,sizeof(*b));
diff --git a/io/iob_send.c b/io/iob_send.c
index 30e12c7..17bff80 100644
--- a/io/iob_send.c
+++ b/io/iob_send.c
@@ -45,7 +45,7 @@ int64 iob_send(int64 s,io_batch* b) {
   for (i=0; x+i<last; ++i)
     if (x[i].n) break;
 
-  if (x[i].type==FROMBUF || x[i].type==FROMBUF_FREE) {
+  if (x[i].type==FROMBUF || x[i].type==FROMBUF_FREE || x[i].type==FROMBUF_MUNMAP) {
     fprintf(stderr,"found non-sent buffer batch entry at %d\n",i);
     if (x+i+1 < last &&
 	(x[i+1].type==FROMFILE || x[i+1].type==FROMFILE_CLOSE)) {
diff --git a/iob.h b/iob.h
index 4cdbe1d..1a37635 100644
--- a/iob.h
+++ b/iob.h
@@ -24,6 +24,7 @@ typedef struct io_batch {
 io_batch* iob_new(int hint_entries);
 int iob_addbuf(io_batch* b,const void* buf,uint64 n);
 int iob_addbuf_free(io_batch* b,const void* buf,uint64 n);
+int iob_addbuf_munmap(io_batch* b,const void* buf,uint64 n);
 int iob_adds(io_batch* b,const char* s);
 int iob_adds_free(io_batch* b,const char* s);
 int iob_addfile(io_batch* b,int64 fd,uint64 off,uint64 n);
diff --git a/iob_internal.h b/iob_internal.h
index d14b879..5c0026c 100644
--- a/iob_internal.h
+++ b/iob_internal.h
@@ -2,7 +2,7 @@
 #include "array.h"
 
 typedef struct iob_entry {
-  enum { FROMBUF, FROMBUF_FREE, FROMFILE, FROMFILE_CLOSE } type;
+  enum { FROMBUF, FROMBUF_FREE, FROMBUF_MUNMAP, FROMFILE, FROMFILE_CLOSE } type;
   int64 fd;
   const char* buf;
   uint64 offset,n;