diff --git a/rtgui/lensgeom.cc b/rtgui/lensgeom.cc
index 69c4737bc6..1d39ced424 100644
--- a/rtgui/lensgeom.cc
+++ b/rtgui/lensgeom.cc
@@ -43,6 +43,11 @@ LensGeometry::LensGeometry () : FoldableToolPanel(this, "lensgeom", M("TP_LENSGE
     show_all ();
 }
 
+LensGeometry::~LensGeometry ()
+{
+    g_idle_remove_by_data(this);
+}
+
 void LensGeometry::read (const ProcParams* pp, const ParamsEdited* pedited)
 {
 
@@ -113,3 +118,26 @@ void LensGeometry::setBatchMode (bool batchMode)
     ToolPanel::setBatchMode (batchMode);
     removeIfThere (this, autoCrop);
 }
+
+void LensGeometry::disableAutoFillIfActive ()
+{
+    g_idle_add(doDisableAutoFillIfActive, this);
+}
+
+int LensGeometry::doDisableAutoFillIfActive (void* data)
+{
+    GThreadLock lock; // Is this really needed?
+
+    LensGeometry* const instance = static_cast<LensGeometry*>(data);
+
+    if (!instance->batchMode) {
+        if (instance->fill->get_active()) {
+            instance->fillConn.block (true);
+            instance->fill->set_active(false);
+            if (instance->listener) {
+                instance->listener->panelChanged (EvTransAutoFill, M("GENERAL_DISABLED"));
+            }
+            instance->fillConn.block (false);
+        }
+    }
+}
diff --git a/rtgui/lensgeom.h b/rtgui/lensgeom.h
index f6b41b632c..51a6e108c0 100644
--- a/rtgui/lensgeom.h
+++ b/rtgui/lensgeom.h
@@ -32,11 +32,12 @@ class LensGeometry : public ToolParamBlock, public FoldableToolPanel
     Gtk::CheckButton*   fill;
     bool                lastFill;
     sigc::connection    fillConn;
-    ToolParamBlock*           packBox;
+    ToolParamBlock*     packBox;
 
 public:
 
     LensGeometry ();
+    ~LensGeometry ();
 
     Gtk::Box* getPackBox ()
     {
@@ -53,6 +54,11 @@ class LensGeometry : public ToolParamBlock, public FoldableToolPanel
     {
         rlistener = l;
     }
+    void disableAutoFillIfActive ();
+
+private:
+    static int doDisableAutoFillIfActive (void* data);
+
 };
 
 #endif
diff --git a/rtgui/lensprofile.cc b/rtgui/lensprofile.cc
index eda3992c34..5555d6dd71 100644
--- a/rtgui/lensprofile.cc
+++ b/rtgui/lensprofile.cc
@@ -142,6 +142,10 @@ void LensProfilePanel::write( rtengine::procparams::ProcParams* pp, ParamsEdited
 
 void LensProfilePanel::onLCPFileChanged()
 {
+
+    // Disable Auto-Fill when enabling LCP Distortion Correction, #1791
+    lensgeomLcpFill->disableAutoFillIfActive();
+
     lcpFileChanged = true;
     updateDisabled(lcpStore->isValidLCPFileName(fcbLCPFile->get_filename()));
 
@@ -164,6 +168,12 @@ void LensProfilePanel::onLCPFileReset()
 
 void LensProfilePanel::onUseDistChanged()
 {
+
+    // Disable Auto-Fill when enabling LCP Distortion Correction, #1791
+    if (ckbUseDist->get_active()) {
+        lensgeomLcpFill->disableAutoFillIfActive();
+    }
+
     useDistChanged = true;
 
     if (listener) {
diff --git a/rtgui/lensprofile.h b/rtgui/lensprofile.h
index 0397388d5a..23d02b9a2e 100644
--- a/rtgui/lensprofile.h
+++ b/rtgui/lensprofile.h
@@ -22,6 +22,7 @@
 #include <gtkmm.h>
 #include "toolpanel.h"
 #include "guiutils.h"
+#include "lensgeom.h"
 
 class LensProfilePanel : public ToolParamBlock, public FoldableToolPanel
 {
@@ -38,6 +39,7 @@ class LensProfilePanel : public ToolParamBlock, public FoldableToolPanel
     void updateDisabled(bool enable);
     bool allowFocusDep;
     bool isRaw;
+    LensGeometry *lensgeomLcpFill;
 
 public:
 
@@ -52,6 +54,7 @@ class LensProfilePanel : public ToolParamBlock, public FoldableToolPanel
     void onUseDistChanged();
     void onUseVignChanged();
     void onUseCAChanged();
+    void setLensGeomRef( LensGeometry *foo) { lensgeomLcpFill = foo ;};
 };
 
 #endif
diff --git a/rtgui/myflatcurve.cc b/rtgui/myflatcurve.cc
index fe53565d2d..0bc3bd5333 100644
--- a/rtgui/myflatcurve.cc
+++ b/rtgui/myflatcurve.cc
@@ -1807,6 +1807,7 @@ void MyFlatCurve::setPoints (const std::vector<double>& p)
     stopNumericalAdjustment();
     FlatCurveType t = (FlatCurveType)p[ix++];
     curve.type = t;
+    lit_point = -1;
 
     if (t == FCT_MinMaxCPoints) {
         curve.x.clear ();
diff --git a/rtgui/toolpanelcoord.cc b/rtgui/toolpanelcoord.cc
index a9f78273e3..a130730189 100644
--- a/rtgui/toolpanelcoord.cc
+++ b/rtgui/toolpanelcoord.cc
@@ -53,6 +53,7 @@ ToolPanelCoordinator::ToolPanelCoordinator () : ipc(nullptr), editDataProvider(n
     colortoning         = Gtk::manage (new ColorToning ());
     lensgeom            = Gtk::manage (new LensGeometry ());
     lensProf            = Gtk::manage (new LensProfilePanel ());
+    lensProf->setLensGeomRef(lensgeom);
     distortion          = Gtk::manage (new Distortion ());
     rotate              = Gtk::manage (new Rotate ());
     vibrance            = Gtk::manage (new Vibrance ());