diff --git a/src/ChFi3d/ChFi3d_Builder_C1.cxx b/src/ChFi3d/ChFi3d_Builder_C1.cxx
index 5125920ba9..401cec0fb9 100644
--- a/src/ChFi3d/ChFi3d_Builder_C1.cxx
+++ b/src/ChFi3d/ChFi3d_Builder_C1.cxx
@@ -371,29 +371,30 @@ static Standard_Boolean Update(Handle(Adaptor3d_HSurface)& face,
     pared = ponc1.Parameter();
     parltg = ponc2.Parameter();
     if ((parltg > f) && (parltg < l)) {
-#ifdef OCC23139
-      ////modified by jgv, 10.05.2012 for the bug 23139////
+      ////modified by jgv, 10.05.2012 for the bug 23139, 25657////
       Handle(Geom2d_Curve) PConF = fi.PCurveOnFace();
       if (!PConF.IsNull())
       {
         Handle(Geom2d_TrimmedCurve) aTrCurve = Handle(Geom2d_TrimmedCurve)::DownCast(PConF);
         if (!aTrCurve.IsNull())
           PConF = aTrCurve->BasisCurve();
-        if (isfirst)
+        if (!PConF->IsPeriodic())
         {
-          Standard_Real fpar = PConF->FirstParameter();
-          if (parltg < fpar)
-            parltg = fpar;
-        }
-        else
-        {
-          Standard_Real lpar = PConF->LastParameter();
-          if (parltg > lpar)
-            parltg = lpar;
+          if (isfirst)
+          {
+            Standard_Real fpar = PConF->FirstParameter();
+            if (parltg < fpar)
+              parltg = fpar;
+          }
+          else
+          {
+            Standard_Real lpar = PConF->LastParameter();
+            if (parltg > lpar)
+              parltg = lpar;
+          }
         }
       }
       /////////////////////////////////////////////////////
-#endif
       fi.SetParameter(parltg,isfirst);
       cp.SetArc(cp.Tolerance(),cp.Arc(),pared,cp.TransitionOnArc());
       return Standard_True;
diff --git a/tests/bugs/modalg_5/bug25657 b/tests/bugs/modalg_5/bug25657
new file mode 100644
index 0000000000..61bb47f45b
--- /dev/null
+++ b/tests/bugs/modalg_5/bug25657
@@ -0,0 +1,25 @@
+puts "========"
+puts "OCC25657"
+puts "========"
+puts ""
+###########################################################################################
+#  Bad result of Fillet operation
+###########################################################################################
+
+restore [locate_data_file bug25657_r4.brep] r4
+explode r4 e
+shape c c
+add r4_15 c
+fillet res r4 20 c
+
+explode res f
+
+pcurve res_2
+# exception
+
+pcurve res_5
+# exception
+
+smallview
+fit
+set only_screen_axo 1
diff --git a/tests/bugs/modalg_5/bug25657_1 b/tests/bugs/modalg_5/bug25657_1
new file mode 100644
index 0000000000..a3436b725a
--- /dev/null
+++ b/tests/bugs/modalg_5/bug25657_1
@@ -0,0 +1,16 @@
+puts "========"
+puts "OCC25657"
+puts "========"
+puts ""
+###########################################################################################
+#  Bad result of Fillet operation
+###########################################################################################
+
+pcylinder a1 140 220
+pcylinder a2 206 120
+ttranslate a2 100 100 120
+bcut a a1 a2
+explode a e
+donly a a_9
+
+blend result a 20 a_9