diff --git a/src/rtkpos.c b/src/rtkpos.c
index f14077aaa..9acc87a7f 100644
--- a/src/rtkpos.c
+++ b/src/rtkpos.c
@@ -1,7 +1,7 @@
 /*------------------------------------------------------------------------------
 * rtkpos.c : precise positioning
 *
-*          Copyright (C) 2007-2013 by T.TAKASU, All rights reserved.
+*          Copyright (C) 2007-2018 by T.TAKASU, All rights reserved.
 *
 * version : $Revision: 1.1 $ $Date: 2008/07/17 21:48:06 $
 * history : 2007/01/12 1.0  new
@@ -34,6 +34,7 @@
 *           2014/10/21 1.16 fix bug on beidou amb-res with pos2-bdsarmode=0
 *           2014/11/08 1.17 fix bug on ar-degradation by unhealthy satellites
 *           2015/03/23 1.18 residuals referenced to reference satellite
+*           2018/01/29 1.19 unfix ambiguity between gps and qzss
 *-----------------------------------------------------------------------------*/
 #include <stdarg.h>
 #include "rtklib.h"
@@ -1004,12 +1005,12 @@ static double gloicbcorr(int sat1, int sat2, const prcopt_t *opt, double lam1,
     
     return opt->exterr.gloicb[f]*0.01*dfreq; /* (m) */
 }
-/* test navi system (m=0:gps/qzs/sbs,1:glo,2:gal,3:bds) ----------------------*/
+/* test navi system (m=0:gps/sbs,1:glo,2:gal,3:bds,4:qzs) --------------------*/
 static int test_sys(int sys, int m)
 {
     switch (sys) {
         case SYS_GPS: return m==0;
-        case SYS_QZS: return m==0;
+        case SYS_QZS: return m==4;
         case SYS_SBS: return m==0;
         case SYS_GLO: return m==1;
         case SYS_GAL: return m==2;
@@ -1049,7 +1050,7 @@ static int ddres(rtk_t *rtk, const nav_t *nav, double dt, const double *x,
             tropr[i]=prectrop(rtk->sol.time,posr,1,azel+ir[i]*2,opt,x,dtdxr+i*3);
         }
     }
-    for (m=0;m<4;m++) /* m=0:gps/qzs/sbs,1:glo,2:gal,3:bds */
+    for (m=0;m<5;m++) /* m=0:gps/sbs,1:glo,2:gal,3:bds,4:qzs */
     
     for (f=opt->mode>PMODE_DGPS?0:nf;f<nf*2;f++) {
         
@@ -1248,7 +1249,7 @@ static int ddmat(rtk_t *rtk, double *D)
     }
     for (i=0;i<na;i++) D[i+i*nx]=1.0;
     
-    for (m=0;m<4;m++) { /* m=0:gps/qzs/sbs,1:glo,2:gal,3:bds */
+    for (m=0;m<5;m++) { /* m=0:gps/sbs,1:glo,2:gal,3:bds,4:qzs */
         
         if (m==1&&rtk->opt.glomodear==0) continue;
         if (m==3&&rtk->opt.bdsmodear==0) continue;
@@ -1297,7 +1298,7 @@ static void restamb(rtk_t *rtk, const double *bias, int nb, double *xa)
     for (i=0;i<rtk->nx;i++) xa[i]=rtk->x [i];
     for (i=0;i<rtk->na;i++) xa[i]=rtk->xa[i];
     
-    for (m=0;m<4;m++) for (f=0;f<nf;f++) {
+    for (m=0;m<5;m++) for (f=0;f<nf;f++) {
         
         for (n=i=0;i<MAXSAT;i++) {
             if (!test_sys(rtk->ssat[i].sys,m)||rtk->ssat[i].fix[f]!=2) {
@@ -1324,7 +1325,7 @@ static void holdamb(rtk_t *rtk, const double *xa)
     
     v=mat(nb,1); H=zeros(nb,rtk->nx);
     
-    for (m=0;m<4;m++) for (f=0;f<nf;f++) {
+    for (m=0;m<5;m++) for (f=0;f<nf;f++) {
         
         for (n=i=0;i<MAXSAT;i++) {
             if (!test_sys(rtk->ssat[i].sys,m)||rtk->ssat[i].fix[f]!=2||