diff --git a/gc.c b/gc.c
index ac716d75..b8689d33 100644
--- a/gc.c
+++ b/gc.c
@@ -1360,13 +1360,14 @@ void gc_thread_data_free(gc_thread_data *thd)
   }
 }
 
-void gc_set_thread_state_blocked(gc_thread_data *thd)
+void gc_set_thread_blocked(gc_thread_data *thd, object cont)
 {
   ATOMIC_SET_IF_EQ(&(thd->thread_state), 
                    CYC_THREAD_STATE_RUNNABLE,
                    CYC_THREAD_STATE_BLOCKED);
+  thd->gc_cont = cont;
 }
-void gc_set_thread_state_runnable(gc_thread_data *thd)
+void gc_set_thread_runnable(gc_thread_data *thd)
 {
   ATOMIC_SET_IF_EQ(&(thd->thread_state), 
                    CYC_THREAD_STATE_BLOCKED, 
diff --git a/include/cyclone/types.h b/include/cyclone/types.h
index cffa9309..467670f1 100644
--- a/include/cyclone/types.h
+++ b/include/cyclone/types.h
@@ -441,8 +441,8 @@ void gc_handshake(gc_status_type s);
 void gc_post_handshake(gc_status_type s);
 void gc_wait_handshake();
 void gc_start_collector();
-void gc_set_thread_state_blocked(gc_thread_data *thd);
-void gc_set_thread_state_runnable(gc_thread_data *thd);
+void gc_set_thread_blocked(gc_thread_data *thd, object cont);
+void gc_set_thread_runnable(gc_thread_data *thd);
 gc_heap *gc_get_heap();
 int gc_minor(void *data, object low_limit, object high_limit, closure cont, object *args, int num_args);
 
diff --git a/runtime.c b/runtime.c
index 25332bad..596a3fba 100644
--- a/runtime.c
+++ b/runtime.c
@@ -1490,9 +1490,9 @@ object Cyc_io_read_char(void *data, object cont, object port) {
     int c;
     Cyc_check_port(data, port);
     {
-        gc_set_thread_state_blocked((gc_thread_data *)data);
+        gc_set_thread_blocked((gc_thread_data *)data, cont);
         c = fgetc(((port_type *) port)->fp);
-        gc_set_thread_state_runnable((gc_thread_data *)data);
+        gc_set_thread_runnable((gc_thread_data *)data);
         if (c != EOF) {
             return obj_char2obj(c);
         }
@@ -1506,17 +1506,17 @@ object Cyc_io_read_line(void *data, object cont, object port) {
   char buf[1024];
   int i = 0, c;
   
-  gc_set_thread_state_blocked((gc_thread_data *)data);
+  gc_set_thread_blocked((gc_thread_data *)data, cont);
   while (1) {
     c = fgetc(stream);
     if (c == EOF && i == 0) {
-      gc_set_thread_state_runnable((gc_thread_data *)data);
+      gc_set_thread_runnable((gc_thread_data *)data);
       return_closcall1(data, cont, Cyc_EOF);
     } else if (c == EOF || i == 1023 || c == '\n') {
       buf[i] = '\0';
       {
         make_string(s, buf);
-        gc_set_thread_state_runnable((gc_thread_data *)data);
+        gc_set_thread_runnable((gc_thread_data *)data);
         return_closcall1(data, cont, &s);
       }
     }
@@ -1533,10 +1533,10 @@ object Cyc_io_peek_char(void *data, object cont, object port) {
     Cyc_check_port(data, port);
     {
         stream = ((port_type *) port)->fp;
-        gc_set_thread_state_blocked((gc_thread_data *)data);
+        gc_set_thread_blocked((gc_thread_data *)data, cont);
         c = fgetc(stream);
         ungetc(c, stream);
-        gc_set_thread_state_runnable((gc_thread_data *)data);
+        gc_set_thread_runnable((gc_thread_data *)data);
         if (c != EOF) {
             return obj_char2obj(c);
         }