diff --git a/vcg/space/color4.h b/vcg/space/color4.h
index a16381da..bcc31a53 100644
--- a/vcg/space/color4.h
+++ b/vcg/space/color4.h
@@ -180,6 +180,8 @@ public:
         (*this)[3]=255;
         return;
       }
+      float dummy;
+      h = modff(h,&dummy);
       if(h==1.0) h = 0.0;
 
       int i   = int( floor(h*6.0) );