Upgrading imagemagick to >6.4 breaks compatibility to rmagick below version 2. RMagick below version 2 should include a depend to block imagemagick from updating to 6.4 or higher. RMagick above version 2 instead requires imagemagick above 6.4. Not upgrading both makes rmagick installation break and emerging rmagick then for rebuilding does not pass the configure phase. Reproducible: Always
*** This bug has been marked as a duplicate of bug 230339 ***