diff --git a/include/picrin/blob.h b/include/picrin/blob.h
index 6b52d9e3..f61f588d 100644
--- a/include/picrin/blob.h
+++ b/include/picrin/blob.h
@@ -18,7 +18,7 @@ struct pic_blob {
 #define pic_blob_p(v) (pic_type(v) == PIC_TT_BLOB)
 #define pic_blob_ptr(v) ((struct pic_blob *)pic_ptr(v))
 
-struct pic_blob *pic_blob_new(pic_state *, char *, size_t len);
+struct pic_blob *pic_blob_new(pic_state *, size_t);
 
 #if defined(__cplusplus)
 }
diff --git a/src/blob.c b/src/blob.c
index 384858aa..efb33ff2 100644
--- a/src/blob.c
+++ b/src/blob.c
@@ -25,12 +25,12 @@ pic_strdup(pic_state *pic, const char *s)
 }
 
 struct pic_blob *
-pic_blob_new(pic_state *pic, char *dat, size_t len)
+pic_blob_new(pic_state *pic, size_t len)
 {
   struct pic_blob *bv;
 
   bv = (struct pic_blob *)pic_obj_alloc(pic, sizeof(struct pic_blob), PIC_TT_BLOB);
-  bv->data = pic_strndup(pic, dat, len);
+  bv->data = pic_alloc(pic, len);
   bv->len = len;
   return bv;
 }
@@ -48,20 +48,20 @@ pic_blob_bytevector_p(pic_state *pic)
 static pic_value
 pic_blob_make_bytevector(pic_state *pic)
 {
+  pic_blob *blob;
   int k, b = 0, i;
-  char *dat;
 
   pic_get_args(pic, "i|i", &k, &b);
 
   if (b < 0 || b > 255)
     pic_error(pic, "byte out of range");
 
-  dat = pic_alloc(pic, k);
+  blob = pic_blob_new(pic, k);
   for (i = 0; i < k; ++i) {
-    dat[i] = b;
+    blob->data[i] = b;
   }
 
-  return pic_obj_value(pic_blob_new(pic, dat, k));
+  return pic_obj_value(blob);
 }
 
 static pic_value
diff --git a/src/port.c b/src/port.c
index 8a3534bc..6f9b6673 100644
--- a/src/port.c
+++ b/src/port.c
@@ -354,8 +354,8 @@ static pic_value
 pic_port_get_output_bytevector(pic_state *pic)
 {
   struct pic_port *port = pic_stdout(pic);
+  pic_blob *blob;
   long endpos;
-  char *buf;
 
   pic_get_args(pic, "|p", &port);
 
@@ -367,10 +367,10 @@ pic_port_get_output_bytevector(pic_state *pic)
   xrewind(port->file);
 
   /* copy to buf */
-  buf = (char *)pic_alloc(pic, endpos);
-  xfread(buf, 1, endpos, port->file);
+  blob = pic_blob_new(pic, endpos);
+  xfread(blob->data, 1, endpos, port->file);
 
-  return pic_obj_value(pic_blob_new(pic, buf, endpos));
+  return pic_obj_value(blob);
 }
 
 static pic_value
@@ -524,28 +524,32 @@ pic_port_byte_ready_p(pic_state *pic)
 
 
 static pic_value
-pic_port_read_blob(pic_state *pic){
+pic_port_read_blob(pic_state *pic)
+{
   struct pic_port *port = pic_stdin(pic);
+  pic_blob *blob;
   int k, i;
-  char *buf;
 
   pic_get_args(pic, "i|p", &k,  &port);
 
   assert_port_profile(port, PIC_PORT_IN | PIC_PORT_BINARY, PIC_PORT_OPEN, "read-bytevector");
 
-  buf = pic_calloc(pic, k, sizeof(char));
-  i = xfread(buf, sizeof(char), k, port->file);
+  blob = pic_blob_new(pic, k);
+
+  i = xfread(blob->data, sizeof(char), k, port->file);
   if ( i == 0 ) {
     return pic_eof_object();
   }
   else {
-    pic_realloc(pic, buf, i);
-    return pic_obj_value(pic_blob_new(pic, buf, i));
+    pic_realloc(pic, blob->data, i);
+    blob->len = i;
+    return pic_obj_value(blob);
   }
 }
 
 static pic_value
-pic_port_read_blob_ip(pic_state *pic){
+pic_port_read_blob_ip(pic_state *pic)
+{
   struct pic_port *port;
   struct pic_blob *bv;
   int i, n, start, end, len;
@@ -568,7 +572,7 @@ pic_port_read_blob_ip(pic_state *pic){
   i = xfread(buf, sizeof(char), len, port->file);
   memcpy(bv->data + start, buf, i);
   pic_free(pic, buf);
-  
+
   if ( i == 0) {
     return pic_eof_object();
   }
diff --git a/src/read.c b/src/read.c
index 62467ece..d7726471 100644
--- a/src/read.c
+++ b/src/read.c
@@ -438,7 +438,7 @@ static pic_value
 read_unsigned_blob(pic_state *pic, struct pic_port *port, char c)
 {
   int nbits, n;
-  size_t len;
+  size_t len, i;
   char *dat, buf[256];
   pic_blob *blob;
 
@@ -471,7 +471,11 @@ read_unsigned_blob(pic_state *pic, struct pic_port *port, char c)
     c = next(port);
   }
 
-  blob = pic_blob_new(pic, dat, len);
+  blob = pic_blob_new(pic, len);
+  for (i = 0; i < len; ++i) {
+    blob->data[i] = dat[i];
+  }
+
   pic_free(pic, dat);
   return pic_obj_value(blob);
 }