diff --git a/ctk-0.1.20171224git71799c2-fix_qreal_cast.patch b/ctk-0.1.20171224git71799c2-fix_qreal_cast.patch
new file mode 100644
index 0000000..3984d15
--- /dev/null
+++ b/ctk-0.1.20171224git71799c2-fix_qreal_cast.patch
@@ -0,0 +1,19 @@
+Index: CTK-71799c27da506c899f2ef04b50cd8d454374870d/Libs/Widgets/ctkMaterialPropertyPreviewLabel.cpp
+===================================================================
+--- CTK-71799c27da506c899f2ef04b50cd8d454374870d.orig/Libs/Widgets/ctkMaterialPropertyPreviewLabel.cpp
++++ CTK-71799c27da506c899f2ef04b50cd8d454374870d/Libs/Widgets/ctkMaterialPropertyPreviewLabel.cpp
+@@ -315,10 +315,10 @@ void ctkMaterialPropertyPreviewLabel::dr
+           }
+         else
+           {
+-          rgba = qRgba(static_cast<unsigned char>(qMin(255. * intensity.x() * opacity + qRed(rgba)*(1. - opacity), static_cast<qreal>(255.))),
+-                       static_cast<unsigned char>(qMin(255. * intensity.y() * opacity + qGreen(rgba)*(1. - opacity), static_cast<qreal>(255.))),
+-                       static_cast<unsigned char>(qMin(255. * intensity.z() * opacity + qBlue(rgba)*(1. - opacity), static_cast<qreal>(255.))),
+-                       static_cast<unsigned char>(qMin(255. * opacity + qAlpha(rgba)*(1. - opacity), static_cast<qreal>(255.))));
++          rgba = qRgba(static_cast<unsigned char>(qMin(static_cast<qreal>(255. * intensity.x() * opacity + qRed(rgba)*(1. - opacity)), static_cast<qreal>(255.))),
++                       static_cast<unsigned char>(qMin(static_cast<qreal>(255. * intensity.y() * opacity + qGreen(rgba)*(1. - opacity)), static_cast<qreal>(255.))),
++                       static_cast<unsigned char>(qMin(static_cast<qreal>(255. * intensity.z() * opacity + qBlue(rgba)*(1. - opacity)), static_cast<qreal>(255.))),
++                       static_cast<unsigned char>(qMin(static_cast<qreal>(255. * opacity + qAlpha(rgba)*(1. - opacity)), static_cast<qreal>(255.))));
+           }
+         }
+       image.setPixel(i,j,rgba);
diff --git a/ctk.spec b/ctk.spec
index def68a9..01cc35b 100644
--- a/ctk.spec
+++ b/ctk.spec
@@ -12,6 +12,8 @@ License:	ASL 2.0
 URL:		http://www.commontk.org
 Source0:	https://github.com/commontk/CTK/archive/%{commit}.tar.gz#/CTK-%{commit}.tar.gz
 
+Patch0:		%{name}-0.1.20171224git71799c2-fix_qreal_cast.patch
+
 BuildRequires:	gcc-c++
 BuildRequires:	cmake
 BuildRequires:	doxygen
@@ -107,7 +109,6 @@ mkdir build
 
 %build
 pushd build
-
 %cmake \
     -DCMAKE_PREFIX_PATH=%{_libdir}/cmake/InsightToolkit \
     -DCTK_SUPERBUILD=OFF \
@@ -118,17 +119,15 @@ pushd build
     -DCTK_ENABLE_DICOM=ON \
     -DCTK_ENABLE_PluginFramework=ON \
     -DCTK_ENABLE_Widgets=ON \
-    -DDOCUMENTATION_TARGET_IN_ALL=ON \
+    -DDOCUMENTATION_TARGET_IN_ALL=OFF \
     ..
-make %{?_smp_mflags}
-
+%make_build
+%make_build doc
 popd
 
 
 %install
-pushd build
-%make_install
-popd
+%make_install -C build
 
 
 # No %%check section here because running tests requires working X server