diff --git a/src/algorithms/libs/rtklib/rtklib_rtksvr.cc b/src/algorithms/libs/rtklib/rtklib_rtksvr.cc
index 6f27b9ca6..e60dbf40a 100644
--- a/src/algorithms/libs/rtklib/rtklib_rtksvr.cc
+++ b/src/algorithms/libs/rtklib/rtklib_rtksvr.cc
@@ -471,7 +471,7 @@ void *rtksvrthread(void *arg)
                     q = svr->buff[i] + svr->buffsize;
 
                     /* read receiver raw/rtcm data from input stream */
-                    if ((n = strread(svr->stream + i, p, q - p)) <= 0)
+                    if ((n = strread(svr->stream + i, p, static_cast<int>(q[0]) - static_cast<int>(p[0]))) <= 0)
                         {
                             continue;
                         }