diff --git a/src/BRepFill/BRepFill_Sweep.cxx b/src/BRepFill/BRepFill_Sweep.cxx
index 8970c4bba3..1eba8dbcb5 100644
--- a/src/BRepFill/BRepFill_Sweep.cxx
+++ b/src/BRepFill/BRepFill_Sweep.cxx
@@ -2969,13 +2969,25 @@ void BRepFill_Sweep::Build(TopTools_MapOfShape& ReversedEdges,
     // Construction of the shell
     TopoDS_Shell shell;
     B.MakeShell(shell);
+    Standard_Integer aNbFaces = 0;
     for (ipath=1; ipath<=NbPath; ipath++) 
-      for (isec=1; isec <=NbLaw; isec++) {
-      const TopoDS_Shape& face = myFaces->Value(isec, ipath);
+      for (isec=1; isec <=NbLaw; isec++)
+      {
+        const TopoDS_Shape& face = myFaces->Value(isec, ipath);
 	if (!face.IsNull() && 
-	    (face.ShapeType() == TopAbs_FACE) ) B.Add(shell, face);
+	    (face.ShapeType() == TopAbs_FACE) )
+        {
+          B.Add(shell, face);
+          aNbFaces++;
+        }
       }
 
+    if (aNbFaces == 0)
+    {
+      isDone = Standard_False;
+      return;
+    }
+
     TopTools_ListIteratorOfListOfShape It(myAuxShape);
     for (; It.More(); It.Next()) {
        const TopoDS_Shape& face = It.Value();
diff --git a/tests/bugs/modalg_7/bug31984 b/tests/bugs/modalg_7/bug31984
new file mode 100644
index 0000000000..fa1a5519b4
--- /dev/null
+++ b/tests/bugs/modalg_7/bug31984
@@ -0,0 +1,12 @@
+puts "=============================================="
+puts "	0031984: Sweep crashes if Bi-normal is given"
+puts "=============================================="
+puts ""
+
+restore [locate_data_file bug31984.brep] a
+explode a
+
+mksweep a_1
+addsweep a_2
+setsweep -CN 0 0 1
+buildsweep result