diff --git a/lcl/interfaces/gtk/gtkobject.inc b/lcl/interfaces/gtk/gtkobject.inc
index 22b0288373..551cd3f001 100644
--- a/lcl/interfaces/gtk/gtkobject.inc
+++ b/lcl/interfaces/gtk/gtkobject.inc
@@ -2303,7 +2303,7 @@ begin
   end;
   try
     // the minimum alignment we can detect is bpp
-    // that is no problem since a line consists of n x bpp pixels
+    // that is no problem since a line consists of n x bytesperpixel bytes
     case Image^.bpl of
       1: Desc^.LineEnd:=rileByteBoundary;
       2: Desc^.LineEnd:=rileWordBoundary;
@@ -2412,7 +2412,8 @@ begin
     // consistency checks
     if NewRawImage.Description.Depth<>AnImage^.Depth then
       RaiseGDBException('NewRawImage.Description.Depth<>AnImage^.Depth '+IntToStr(NewRawImage.Description.Depth)+'<>'+IntToStr(AnImage^.Depth));
-    if NewRawImage.Description.BitsPerPixel<>AnImage^.bpp then
+    //debugln('TGtkWidgetSet.GetRawImageFromGdkWindow  NewRawImage.Description.BitsPerPixel=',dbgs(NewRawImage.Description.BitsPerPixel),' AnImage^.bpp=',dbgs(AnImage^.bpp),' GetPGdkImageBitsPerPixel(AnImage)=',dbgs(GetPGdkImageBitsPerPixel(AnImage)));
+    if NewRawImage.Description.BitsPerPixel<>GetPGdkImageBitsPerPixel(AnImage) then
       RaiseGDBException('NewRawImage.Description.BitsPerPixel<>AnImage^.bpp');
 
     NewRawImage.DataSize:=AnImage^.bpl * AnImage^.Height;
@@ -2496,7 +2497,7 @@ begin
   end;
   try
     {$IFDEF VerboseRawImage}
-    DebugLn('TGTKWidgetSet.GetRawImageMaskFromGdkBitmap A BytesPerLine=',dbgs(AnImage^.bpl),' theType=',dbgs(AnImage^.thetype),' depth=',dbgs(AnImage^.depth),' BitsPerpixel=',dbgs(AnImage^.bpp));
+    DebugLn('TGTKWidgetSet.GetRawImageMaskFromGdkBitmap A BytesPerLine=',dbgs(AnImage^.bpl),' theType=',dbgs(AnImage^.thetype),' depth=',dbgs(AnImage^.depth),' AnImage^.bpp=',dbgs(AnImage^.bpp));
     DebugLn('RawImage=',RawImageDescriptionAsString(@RawImage));
     {$ENDIF}
 
@@ -2507,7 +2508,7 @@ begin
     9..32:  RawImage.Description.AlphaLineEnd:=rileDWordBoundary;// X does not seem to use Word boundaries
     else    RawImage.Description.AlphaLineEnd:=rileQWordBoundary;
     end;}
-    RawImage.Description.AlphaBitsPerPixel:=AnImage^.bpp;
+    RawImage.Description.AlphaBitsPerPixel:=GetPGdkImageBitsPerPixel(AnImage);
 
     // consistency checks
     if RawImage.Description.AlphaBitsPerPixel<>AnImage^.Depth then
diff --git a/lcl/interfaces/gtk/gtkproc.inc b/lcl/interfaces/gtk/gtkproc.inc
index 45c5fbb0b2..6a3d749d13 100644
--- a/lcl/interfaces/gtk/gtkproc.inc
+++ b/lcl/interfaces/gtk/gtkproc.inc
@@ -1362,6 +1362,13 @@ begin
   ReleaseDC(HDC(DestWidget),DestDC);
 end;
 
+function GetPGdkImageBitsPerPixel(Image: PGdkImage): cardinal;
+begin
+  Result:=Image^.bpp;
+  if Result<Image^.Depth then
+    Result:=Result*8;
+end;
+
 function CreateGdkBitmap(Window: PGdkWindow;
   Width, Height: integer): PGdkBitmap;
 var
diff --git a/lcl/interfaces/gtk/gtkproc.pp b/lcl/interfaces/gtk/gtkproc.pp
index c4de88f259..27dac199ae 100644
--- a/lcl/interfaces/gtk/gtkproc.pp
+++ b/lcl/interfaces/gtk/gtkproc.pp
@@ -662,6 +662,7 @@ procedure DrawImageListIconOnWidget(ImgList: TCustomImageList;
   Index: integer; DestWidget: PGTKWidget;
   CenterHorizontally, CenterVertically: boolean;
   DestLeft, DestTop: integer);
+function GetPGdkImageBitsPerPixel(Image: PGdkImage): cardinal;
 {$IfDef Win32}
 Procedure gdk_window_copy_area(Dest: PGDKWindow; GC: PGDKGC;
   DestX, DestY: Longint; SRC: PGDKWindow; XSRC, YSRC, Width, Height: Longint);
diff --git a/lcl/interfaces/gtk/gtkwinapi.inc b/lcl/interfaces/gtk/gtkwinapi.inc
index 2a9d924fa2..65ed92f73c 100644
--- a/lcl/interfaces/gtk/gtkwinapi.inc
+++ b/lcl/interfaces/gtk/gtkwinapi.inc
@@ -1000,11 +1000,11 @@ begin
         {$IFDEF VerboseRawImage}
         DebugLn('TGtkWidgetSet.CreateBitmapFromRawImage GdkImage: ',
           ' BytesPerLine=',dbgs(GdkImage^.bpl),
-          ' BytesPerPixel=',dbgs(GdkImage^.bpp),
+          ' BitsPerPixel=',dbgs(GetPGdkImageBitsPerPixel(GdkImage)),
           ' ByteOrder=',dbgs(GdkImage^.byte_order),
           '');
         {$ENDIF}
-        if (RawImage.Description.BitsPerPixel<>(cardinal(GdkImage^.bpp) shl 3))
+        if (RawImage.Description.BitsPerPixel<>GetPGdkImageBitsPerPixel(GdkImage))
         then begin
           RaiseGDBException('TGtkWidgetSet.CreateBitmapFromRawImage Incompatible BitsPerPixel');
         end;