diff --git a/ctk-qreal_not_double.patch b/ctk-qreal_not_double.patch
new file mode 100644
index 0000000..a2e4088
--- /dev/null
+++ b/ctk-qreal_not_double.patch
@@ -0,0 +1,28 @@
+Index: CTK-bdc8caca0458759e1672a94ca2857595d40f17b0/Libs/Widgets/ctkMaterialPropertyPreviewLabel.cpp
+===================================================================
+--- CTK-bdc8caca0458759e1672a94ca2857595d40f17b0.orig/Libs/Widgets/ctkMaterialPropertyPreviewLabel.cpp
++++ CTK-bdc8caca0458759e1672a94ca2857595d40f17b0/Libs/Widgets/ctkMaterialPropertyPreviewLabel.cpp
+@@ -295,7 +295,7 @@ void ctkMaterialPropertyPreviewLabel::dr
+         ref.setZ( 2.*normal.z()*dot - light.z());
+         ref.normalize();
+ 
+-        qreal diffuseComp = qMax(diffuse * dot, 0.);
++        qreal diffuseComp = qMax<qreal>(diffuse * dot, 0.);
+ 
+         qreal specularDot = qMax(static_cast<qreal>(QVector3D::dotProduct(ref, view)), static_cast<qreal>(0));
+ 
+@@ -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<qreal>(255. * intensity.x() * opacity + qRed(rgba)*(1. - opacity), static_cast<qreal>(255.))),
++                       static_cast<unsigned char>(qMin<qreal>(255. * intensity.y() * opacity + qGreen(rgba)*(1. - opacity), static_cast<qreal>(255.))),
++                       static_cast<unsigned char>(qMin<qreal>(255. * intensity.z() * opacity + qBlue(rgba)*(1. - opacity), static_cast<qreal>(255.))),
++                       static_cast<unsigned char>(qMin<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 659ea0e..49f76d7 100644
--- a/ctk.spec
+++ b/ctk.spec
@@ -11,6 +11,7 @@ Summary:	The Commmon Toolkit for biomedical imaging
 License:	ASL 2.0
 URL:		http://www.commontk.org
 Source0:	https://github.com/commontk/CTK/archive/%{commit}.tar.gz#/CTK-%{commit}.tar.gz
+Patch0:		ctk-qreal_not_double.patch
 
 BuildRequires:	gcc-c++
 BuildRequires:	cmake
@@ -101,7 +102,7 @@ This package contains CTK developer documentation.
 
 
 %prep
-%autosetup -n CTK-%{commit}
+%autosetup -n CTK-%{commit} -p1
 mkdir build