diff --git a/lib/easy.c b/lib/easy.c
index 53f417f..796ff90 100644
--- a/lib/easy.c
+++ b/lib/easy.c
@@ -1120,9 +1120,6 @@ CURLcode curl_easy_recv(CURL *curl, void *buffer, size_t buflen, size_t *n)
   *n = 0;
   ret1 = Curl_read(c, sfd, buffer, buflen, &n1);
 
-  if(ret1 == -1)
-    return CURLE_AGAIN;
-
   if(ret1 != CURLE_OK)
     return (CURLcode)ret1;
 
diff --git a/lib/http.c b/lib/http.c
index fc01ee8..c6a6418 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -1468,8 +1468,7 @@ CURLcode Curl_proxyCONNECT(struct connectdata *conn,
         default:
           DEBUGASSERT(ptr+BUFSIZE-nread <= data->state.buffer+BUFSIZE+1);
           res = Curl_read(conn, tunnelsocket, ptr, BUFSIZE-nread, &gotbytes);
-          if(res< 0)
-            /* EWOULDBLOCK */
+          if(res==CURLE_AGAIN)
             continue; /* go loop yourself */
           else if(res)
             keepon = FALSE;
diff --git a/lib/pingpong.c b/lib/pingpong.c
index c6b6f2f..6172833 100644
--- a/lib/pingpong.c
+++ b/lib/pingpong.c
@@ -340,8 +340,7 @@ CURLcode Curl_pp_readresp(curl_socket_t sockfd,
 #if defined(HAVE_KRB4) || defined(HAVE_GSSAPI)
       conn->data_prot = prot;
 #endif
-      if(res < 0)
-        /* EWOULDBLOCK */
+      if(res == CURLE_AGAIN)
         return CURLE_OK; /* return */
 
 #ifdef CURL_DOES_CONVERSIONS
diff --git a/lib/sendf.c b/lib/sendf.c
index 4843214..1693a46 100644
--- a/lib/sendf.c
+++ b/lib/sendf.c
@@ -238,7 +238,7 @@ CURLcode Curl_sendf(curl_socket_t sockfd, struct connectdata *conn,
  * Curl_write() is an internal write function that sends data to the
  * server. Works with plain sockets, SCP, SSL or kerberos.
  *
- * If the write would block (EWOULDBLOCK), we return CURLE_OK and
+ * If the write would block (CURLE_AGAIN), we return CURLE_OK and
  * (*written == 0). Otherwise we return regular CURLcode value.
  */
 CURLcode Curl_write(struct connectdata *conn,
@@ -258,7 +258,7 @@ CURLcode Curl_write(struct connectdata *conn,
     /* we completely ignore the curlcode value when -1 is not returned */
     return CURLE_OK;
 
-  /* handle EWOULDBLOCK or a send failure */
+  /* handle CURLE_AGAIN or a send failure */
   switch(curlcode) {
   case CURLE_AGAIN:
     *written = 0;
@@ -437,7 +437,7 @@ CURLcode Curl_client_write(struct connectdata *conn,
   return CURLE_OK;
 }
 
-int Curl_read_plain(curl_socket_t sockfd,
+CURLcode Curl_read_plain(curl_socket_t sockfd,
                          char *buf,
                          size_t bytesfromsocket,
                          ssize_t *n)
@@ -451,7 +451,7 @@ int Curl_read_plain(curl_socket_t sockfd,
 #else
     if((EWOULDBLOCK == err) || (EAGAIN == err) || (EINTR == err))
 #endif
-      return -1;
+      return CURLE_AGAIN;
     else
       return CURLE_RECV_ERROR;
   }
@@ -465,10 +465,9 @@ int Curl_read_plain(curl_socket_t sockfd,
  * Internal read-from-socket function. This is meant to deal with plain
  * sockets, SSL sockets and kerberos sockets.
  *
- * If the read would block (EWOULDBLOCK) we return -1. Otherwise we return
- * a regular CURLcode value.
+ * Returns a regular CURLcode value.
  */
-int Curl_read(struct connectdata *conn, /* connection data */
+CURLcode Curl_read(struct connectdata *conn, /* connection data */
               curl_socket_t sockfd,     /* read from this socket */
               char *buf,                /* store read data here */
               size_t sizerequested,     /* max amount to read */
diff --git a/lib/sendf.h b/lib/sendf.h
index 5732a0b..ed3b3a5 100644
--- a/lib/sendf.h
+++ b/lib/sendf.h
@@ -55,13 +55,13 @@ CURLcode Curl_client_write(struct connectdata *conn, int type, char *ptr,
                            size_t len);
 
 /* internal read-function, does plain socket only */
-int Curl_read_plain(curl_socket_t sockfd,
+CURLcode Curl_read_plain(curl_socket_t sockfd,
                     char *buf,
                     size_t bytesfromsocket,
                     ssize_t *n);
 
 /* internal read-function, does plain socket, SSL and krb4 */
-int Curl_read(struct connectdata *conn, curl_socket_t sockfd,
+CURLcode Curl_read(struct connectdata *conn, curl_socket_t sockfd,
               char *buf, size_t buffersize,
               ssize_t *n);
 /* internal write-function, does plain socket, SSL, SCP, SFTP and krb4 */
diff --git a/lib/telnet.c b/lib/telnet.c
index e7f05eb..3bbbc3d 100644
--- a/lib/telnet.c
+++ b/lib/telnet.c
@@ -1384,8 +1384,8 @@ static CURLcode telnet_do(struct connectdata *conn, bool *done)
       if(events.lNetworkEvents & FD_READ) {
         /* read data from network */
         ret = Curl_read(conn, sockfd, buf, BUFSIZE - 1, &nread);
-        /* returned sub-zero, this would've blocked. Loop again */
-        if(ret < 0)
+        /* read would've blocked. Loop again */
+        if(ret == CURLE_AGAIN)
           break;
         /* returned not-zero, this an error */
         else if(ret) {
@@ -1473,8 +1473,8 @@ static CURLcode telnet_do(struct connectdata *conn, bool *done)
       if(pfd[0].revents & POLLIN) {
         /* read data from network */
         ret = Curl_read(conn, sockfd, buf, BUFSIZE - 1, &nread);
-        /* returned sub-zero, this would've blocked. Loop again */
-        if(ret < 0)
+        /* read would've blocked. Loop again */
+        if(ret == CURLE_AGAIN)
           break;
         /* returned not-zero, this an error */
         else if(ret) {
diff --git a/lib/transfer.c b/lib/transfer.c
index 92a59d0..2635582 100644
--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -376,7 +376,7 @@ static CURLcode readwrite_data(struct SessionHandle *data,
   *done = FALSE;
 
   /* This is where we loop until we have read everything there is to
-     read or we get a EWOULDBLOCK */
+     read or we get a CURLE_AGAIN */
   do {
     size_t buffersize = data->set.buffer_size?
       data->set.buffer_size : BUFSIZE;
@@ -396,8 +396,8 @@ static CURLcode readwrite_data(struct SessionHandle *data,
       /* receive data from the network! */
       readrc = Curl_read(conn, conn->sockfd, k->buf, bytestoread, &nread);
 
-      /* subzero, this would've blocked */
-      if(0 > readrc)
+      /* read would've blocked */
+      if(CURLE_AGAIN == readrc)
         break; /* get out of loop */
 
       /* get the CURLcode from the int */