diff --git a/gc.c b/gc.c
index 455499e9..0d039693 100644
--- a/gc.c
+++ b/gc.c
@@ -495,6 +495,8 @@ char *gc_copy_obj(object dest, char *obj, gc_thread_data * thd)
       hp->tok_buf_len = ((port_type *) obj)->tok_buf_len;
       hp->mem_buf = ((port_type *)obj)->mem_buf;
       hp->mem_buf_len = ((port_type *)obj)->mem_buf_len;
+      hp->str_bv_in_mem_buf = ((port_type *)obj)->str_bv_in_mem_buf;
+      hp->str_bv_in_mem_buf_len = ((port_type *)obj)->str_bv_in_mem_buf_len;
       hp->read_len = ((port_type *)obj)->read_len;
       return (char *)hp;
     }
diff --git a/include/cyclone/types.h b/include/cyclone/types.h
index 6069550a..846c0360 100644
--- a/include/cyclone/types.h
+++ b/include/cyclone/types.h
@@ -789,6 +789,8 @@ typedef struct {
   char *mem_buf;
   size_t mem_buf_len;
   unsigned short read_len;
+  char *str_bv_in_mem_buf;
+  char *str_bv_in_mem_buf_len;
 } port_type;
 
 #define CYC_IO_BUF_LEN 1024
diff --git a/runtime.c b/runtime.c
index 730041b8..cd25bd04 100644
--- a/runtime.c
+++ b/runtime.c
@@ -3444,6 +3444,11 @@ object Cyc_io_close_port(void *data, object port)
       ((port_type *)port)->mem_buf = NULL;
       ((port_type *)port)->mem_buf_len = 0;
     }
+    if (((port_type *)port)->str_bv_in_mem_buf != NULL){
+      free( ((port_type *)port)->str_bv_in_mem_buf );
+      ((port_type *)port)->str_bv_in_mem_buf = NULL;
+      ((port_type *)port)->str_bv_in_mem_buf_len = 0;
+    }
     if (((port_type *)port)->tok_buf != NULL){
       free( ((port_type *)port)->tok_buf );
       ((port_type *)port)->tok_buf = NULL;