diff --git a/init.g b/init.g
index 4801060..2e70fd9 100644
--- a/init.g
+++ b/init.g
@@ -28,6 +28,22 @@ if not IsBound(MultVector) then
     DeclareSynonym( "MultVector", MultRowVector );
 fi;
 
+#
+# GAP >= 4.17 has unchecked NC variants of the PreImages operations
+#
+if not IsBound( PreImagesNC ) then
+    BindGlobal( "PreImagesNC", PreImages );
+fi;
+if not IsBound( PreImagesElmNC ) then
+    BindGlobal( "PreImagesElmNC", PreImagesElm );
+fi;
+if not IsBound( PreImagesSetNC ) then
+    BindGlobal( "PreImagesSetNC", PreImagesSet );
+fi;
+if not IsBound( PreImagesRepresentativeNC ) then
+    BindGlobal( "PreImagesRepresentativeNC", PreImagesRepresentative );
+fi;
+
 ReadPackage("fining","lib/geometry.gd");
 
 ReadPackage("fining","lib/liegeometry.gd");
diff --git a/lib/gpolygons.gi b/lib/gpolygons.gi
index c8014fc..69989da 100644
--- a/lib/gpolygons.gi
+++ b/lib/gpolygons.gi
@@ -4020,7 +4020,7 @@ InstallMethod( EGQByBLTSet,
                                        [0,0,0,1,0,0],[0,0,0,0,1,0]]*One(f));
     q4qcanonical := Range(duality)!.geometry;
     iso := IsomorphismPolarSpaces(q4q, q4qcanonical);
-    bltdual := PreImagesSet(duality, ImagesSet(iso, blt));
+    bltdual := PreImagesSetNC(duality, ImagesSet(iso, blt));
 
     Info(InfoFinInG, 1, "Now embedding dual BLT-set into W(5,q)...");
 
@@ -4301,7 +4301,7 @@ InstallMethod( FlockGQByqClan, [ IsqClanObj ],
   imgs := Filtered([1..Size(omega)], x -> omega[x] in blt);;
   stabblt := Stabilizer(Image(hom), imgs, OnSets);
   gens := GeneratorsOfGroup(stabblt);
-  gens := List(gens, x -> PreImagesRepresentative(hom, x));
+  gens := List(gens, x -> PreImagesRepresentativeNC(hom, x));
   stabblt := GroupWithGenerators(gens);
 
   Info(InfoFinInG, 1, "..computed stabiliser of BLT set");
diff --git a/lib/morphisms.gi b/lib/morphisms.gi
index bbc585e..77dc81d 100644
--- a/lib/morphisms.gi
+++ b/lib/morphisms.gi
@@ -204,15 +204,25 @@ InstallOtherMethod( PreImageElm,
 
 # CHECKED 27/09/11 jdb
 #############################################################################
-#O  PreImagesSet( <em>, <x> )
+#O  PreImagesSetNC( <em>, <x> )
 ##
-InstallOtherMethod( PreImagesSet,
+InstallOtherMethod( PreImagesSetNC,
     "for a geometry morphism and an element of an incidence structure",
     [IsGeometryMorphism, IsElementOfIncidenceStructureCollection],
     function(em, x)
         return List(x, t -> em!.prefun(t));
     end );
 
+# The generic PreImagesSet fails its IsSubset( Range( em ), x ) check for
+# geometry morphisms. Without PreImagesSetNC in GAP, both names denote the
+# same operation, see init.g.
+if not IsIdenticalObj( PreImagesSet, PreImagesSetNC ) then
+    InstallOtherMethod( PreImagesSet,
+        "for a geometry morphism and an element of an incidence structure",
+        [IsGeometryMorphism, IsElementOfIncidenceStructureCollection],
+        PreImagesSetNC );
+fi;
+
 ##########################################################
 ## User methods for the "natural geometry morphisms"
 ##########################################################
diff --git a/lib/orbits-stabilisers.gi b/lib/orbits-stabilisers.gi
index e6174af..8d0f753 100644
--- a/lib/orbits-stabilisers.gi
+++ b/lib/orbits-stabilisers.gi
@@ -411,7 +411,7 @@ InstallMethod( FiningStabiliserPerm, [IsProjectiveGroupWithFrob, IsElementOfInci
         nr:=Position(enum,el);
         stab:=Stabilizer(Image(hom),nr);
         gens:=GeneratorsOfGroup(stab);;
-        gens:=List(gens,x->PreImagesRepresentative(hom,x));
+        gens:=List(gens,x->PreImagesRepresentativeNC(hom,x));
         stab:=GroupWithGenerators(gens);
         return stab;
 end );
@@ -433,7 +433,7 @@ InstallMethod( FiningStabiliserPerm2,
         stab:=Stab(im,nr,OnPoints,rec( DoEstimate := size )).stab;
         #stab:=Stabiliser(Image(hom),nr);
         gens:=GeneratorsOfGroup(stab);;
-        gens:=List(gens,x->PreImagesRepresentative(hom,x));
+        gens:=List(gens,x->PreImagesRepresentativeNC(hom,x));
         stab:=GroupWithGenerators(gens);
         return stab;
 end );
diff --git a/tst/bugfix.tst b/tst/bugfix.tst
index 413e85e..75a7986 100644
--- a/tst/bugfix.tst
+++ b/tst/bugfix.tst
@@ -20,5 +20,13 @@ gap> ElationOfProjectiveSpace(l, p, q);
 gap> SingerCycleCollineation(2, 2^6);
 < a collineation: <cmat 3x3 over GF(2,6)>, F^0>
 
+# GAP >= 4.17 calls PreImagesSetNC internally
+gap> d := NaturalDuality(SymplecticSpace(3, 3));;
+gap> pts := AsList(Points(Range(d)!.geometry)){[1..3]};;
+gap> PreImagesSetNC(d, pts) = List(pts, x -> PreImageElm(d, x));
+true
+gap> PreImagesSet(d, pts) = PreImagesSetNC(d, pts);
+true
+
 #
 gap> STOP_TEST("bugfix.tst", 1 );