diff --git a/rtengine/capturesharpening.cc b/rtengine/capturesharpening.cc
index a080b4f36..63c42026e 100644
--- a/rtengine/capturesharpening.cc
+++ b/rtengine/capturesharpening.cc
@@ -22,7 +22,6 @@
 #include "rtengine.h"
 #include "rawimagesource.h"
 #include "rt_math.h"
-#include "improcfun.h"
 #include "procparams.h"
 #include "color.h"
 #include "gauss.h"
@@ -605,13 +604,13 @@ BENCHFUN
                     // special handling for small tiles at end of row or column
                     for (int k = border, ii = endOfCol ? H - fullTileSize - border : i - border; k < fullTileSize - border; ++k) {
                         for (int l = border, jj = endOfRow ? W - fullTileSize - border : j - border; l < fullTileSize - border; ++l) {
-                            luminance[ii + k][jj + l] = rtengine::intp(blend[ii + k][jj + l], max(tmpIThr[k][l], 0.0f), luminance[ii + k][jj + l]);
+                            luminance[ii + k][jj + l] = rtengine::intp(blend[ii + k][jj + l], std::max(tmpIThr[k][l], 0.0f), luminance[ii + k][jj + l]);
                         }
                     }
                 } else {
                     for (int ii = border; ii < fullTileSize - border; ++ii) {
                         for (int jj = border; jj < fullTileSize - border; ++jj) {
-                            luminance[i + ii - border][j + jj - border] = rtengine::intp(blend[i + ii - border][j + jj - border], max(tmpIThr[ii][jj], 0.0f), luminance[i + ii - border][j + jj - border]);
+                            luminance[i + ii - border][j + jj - border] = rtengine::intp(blend[i + ii - border][j + jj - border], std::max(tmpIThr[ii][jj], 0.0f), luminance[i + ii - border][j + jj - border]);
                         }
                     }
                 }
diff --git a/rtengine/curves.h b/rtengine/curves.h
index 25272d44c..b4c1b54d4 100644
--- a/rtengine/curves.h
+++ b/rtengine/curves.h
@@ -16,8 +16,7 @@
  *  You should have received a copy of the GNU General Public License
  *  along with RawTherapee.  If not, see <https://www.gnu.org/licenses/>.
  */
-#ifndef __CURVES_H__
-#define __CURVES_H__
+#pragma once
 
 #include <map>
 #include <string>
@@ -1311,5 +1310,3 @@ inline void SatAndValueBlendingToneCurve::Apply (float& ir, float& ig, float& ib
 }
 
 #undef CLIPI
-
-#endif
diff --git a/rtengine/dcp.cc b/rtengine/dcp.cc
index 6376968e6..9fac31c99 100644
--- a/rtengine/dcp.cc
+++ b/rtengine/dcp.cc
@@ -28,7 +28,6 @@
 #include "iccmatrices.h"
 #include "iccstore.h"
 #include "imagefloat.h"
-#include "improcfun.h"
 #include "rawimagesource.h"
 #include "rt_math.h"
 
diff --git a/rtengine/imagesource.h b/rtengine/imagesource.h
index 0f7a2ff51..8597a8dc3 100644
--- a/rtengine/imagesource.h
+++ b/rtengine/imagesource.h
@@ -33,6 +33,8 @@ namespace rtengine
 {
 class ColorTemp;
 class Imagefloat;
+class RetinextransmissionCurve;
+class RetinexgaintransmissionCurve;
 
 namespace procparams
 {
diff --git a/rtengine/improcfun.cc b/rtengine/improcfun.cc
index e446f21a0..523683002 100644
--- a/rtengine/improcfun.cc
+++ b/rtengine/improcfun.cc
@@ -29,6 +29,7 @@
 #include "rtengine.h"
 #include "improcfun.h"
 #include "curves.h"
+#include "dcp.h"
 #include "mytime.h"
 #include "iccstore.h"
 #include "imagesource.h"
diff --git a/rtengine/improcfun.h b/rtengine/improcfun.h
index b3ba2ccb8..16b8e27b0 100644
--- a/rtengine/improcfun.h
+++ b/rtengine/improcfun.h
@@ -25,12 +25,20 @@
 #include "LUT.h"
 #include "lcp.h"
 #include "dcp.h"
-#include "curves.h"
 #include "pipettebuffer.h"
 #include "gamutwarning.h"
 
 namespace rtengine
 {
+class ColorGradientCurve;
+class OpacityCurve;
+class ToneCurve;
+class WavCurve;
+class WavOpacityCurveRG;
+class WavOpacityCurveBY;
+class WavOpacityCurveW;
+class WavOpacityCurveWL;
+
 class CieImage;
 class Image8;
 class Imagefloat;
diff --git a/rtengine/iplab2rgb.cc b/rtengine/iplab2rgb.cc
index 451a68a3f..4298e41c9 100644
--- a/rtengine/iplab2rgb.cc
+++ b/rtengine/iplab2rgb.cc
@@ -26,7 +26,6 @@
 #include "iccmatrices.h"
 #include "../rtgui/options.h"
 #include "settings.h"
-#include "curves.h"
 #include "alignedbuffer.h"
 #include "color.h"
 #include "procparams.h"
diff --git a/rtengine/rawimagesource.h b/rtengine/rawimagesource.h
index 6c8dff696..771398fa0 100644
--- a/rtengine/rawimagesource.h
+++ b/rtengine/rawimagesource.h
@@ -25,8 +25,6 @@
 #include "array2D.h"
 #include "color.h"
 #include "colortemp.h"
-#include "curves.h"
-#include "dcp.h"
 #include "iimage.h"
 #include "imagesource.h"
 #include "pixelsmap.h"
@@ -36,6 +34,10 @@
 namespace rtengine
 {
 
+class DiagonalCurve;
+class RetinextransmissionCurve;
+class RetinexgaintransmissionCurve;
+
 class RawImageSource : public ImageSource
 {
 private:
diff --git a/rtengine/stdimagesource.cc b/rtengine/stdimagesource.cc
index 43628e074..8e4c05ac8 100644
--- a/rtengine/stdimagesource.cc
+++ b/rtengine/stdimagesource.cc
@@ -19,7 +19,6 @@
 #include "stdimagesource.h"
 
 #include "color.h"
-#include "curves.h"
 #include "iccstore.h"
 #include "image8.h"
 #include "image16.h"
diff --git a/rtgui/navigator.cc b/rtgui/navigator.cc
index de07ffcd7..2cad9fdc1 100644
--- a/rtgui/navigator.cc
+++ b/rtgui/navigator.cc
@@ -21,7 +21,6 @@
 #include "toolpanel.h"
 #include "../rtengine/iccmatrices.h"
 #include "../rtengine/iccstore.h"
-#include "../rtengine/curves.h"
 #include "../rtengine/color.h"
 #include "../rtengine/rt_math.h"
 #include "options.h"