diff --git a/CHANGELOG b/CHANGELOG
index f98b075e..aa9f3100 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -21,6 +21,10 @@ HISTORY
 
  ++ Bugfixes:
 
+  2011-08-24: Simon Goldschmidt
+  * api_msg.c, sockets.c: fixed bug #33956 Wrong error returned when calling
+    accept() on UDP connections
+
   2011-08-24: Simon Goldschmidt
   * sockets.h: fixed bug #34057 socklen_t should be a typedef
 
diff --git a/src/api/api_msg.c b/src/api/api_msg.c
index f9f709e7..76ac49e7 100644
--- a/src/api/api_msg.c
+++ b/src/api/api_msg.c
@@ -1089,6 +1089,8 @@ do_listen(struct api_msg_msg *msg)
             }
           }
         }
+      } else {
+        msg->err = ERR_ARG;
       }
     }
   }
diff --git a/src/api/sockets.c b/src/api/sockets.c
index a9a85c37..e7d8e1e9 100644
--- a/src/api/sockets.c
+++ b/src/api/sockets.c
@@ -336,6 +336,10 @@ lwip_accept(int s, struct sockaddr *addr, socklen_t *addrlen)
   err = netconn_accept(sock->conn, &newconn);
   if (err != ERR_OK) {
     LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_accept(%d): netconn_acept failed, err=%d\n", s, err));
+    if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) != NETCONN_TCP) {
+      sock_set_errno(sock, EOPNOTSUPP);
+      return EOPNOTSUPP;
+    }
     sock_set_errno(sock, err_to_errno(err));
     return -1;
   }
@@ -537,6 +541,10 @@ lwip_listen(int s, int backlog)
 
   if (err != ERR_OK) {
     LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_listen(%d) failed, err=%d\n", s, err));
+    if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) != NETCONN_TCP) {
+      sock_set_errno(sock, EOPNOTSUPP);
+      return EOPNOTSUPP;
+    }
     sock_set_errno(sock, err_to_errno(err));
     return -1;
   }