diff --git a/lib/includes/spdylay/spdylay.h b/lib/includes/spdylay/spdylay.h
index b69f6a85..0a9593cf 100644
--- a/lib/includes/spdylay/spdylay.h
+++ b/lib/includes/spdylay/spdylay.h
@@ -45,6 +45,7 @@ typedef enum {
   SPDYLAY_ERR_WOULDBLOCK = -504,
   SPDYLAY_ERR_PROTO = -505,
   SPDYLAY_ERR_INVALID_FRAME = -506,
+  SPDYLAY_ERR_EOF = -507,
 
   /* The errors < SPDYLAY_ERR_FATAL mean that the library is under
      unexpected condition that it cannot process any further data
@@ -165,6 +166,14 @@ typedef ssize_t (*spdylay_send_callback)
 (spdylay_session *session,
  const uint8_t *data, size_t length, int flags, void *user_data);
 
+/*
+ * Callback function invoked when the library want to read data from
+ * remote peer. The implementation of this function must read at most
+ * |length| bytes of data and store it in |buf|. It must return the
+ * number of bytes written in |buf| if it succeeds. If it gets EOF
+ * before it reads any single byte, return SPDYLAY_ERR_EOF. For other
+ * errors, return SPDYLAY_ERR_CALLBACK_FAILURE.
+ */
 typedef ssize_t (*spdylay_recv_callback)
 (spdylay_session *session,
  uint8_t *buf, size_t length, int flags, void *user_data);
diff --git a/lib/spdylay_session.c b/lib/spdylay_session.c
index 4b74be70..8ddf03ab 100644
--- a/lib/spdylay_session.c
+++ b/lib/spdylay_session.c
@@ -1077,7 +1077,7 @@ int spdylay_session_recv(spdylay_session *session)
       uint32_t payloadlen;
       if(spdylay_inbound_buffer_avail(&session->ibuf) < SPDYLAY_HEAD_LEN) {
         r = spdylay_recv(session);
-        /* TODO handle EOF */
+        /* If EOF is reached, r == SPDYLAY_ERR_EOF */
         if(r < 0) {
           if(r == SPDYLAY_ERR_WOULDBLOCK) {
             return 0;
@@ -1114,12 +1114,10 @@ int spdylay_session_recv(spdylay_session *session)
       if(spdylay_inbound_buffer_avail(&session->ibuf) == 0 &&
          rempayloadlen > 0) {
         r = spdylay_recv(session);
-        if(r <= 0) {
-          if(r == SPDYLAY_ERR_WOULDBLOCK) {
-            return 0;
-          } else {
-            return r;
-          }
+        if(r == 0 || r == SPDYLAY_ERR_WOULDBLOCK) {
+          return 0;
+        } else if(r < 0) {
+          return r;
         }
       }
       bufavail = spdylay_inbound_buffer_avail(&session->ibuf);