diff --git a/includes-ros1/orocos-kinematics-dynamics/orocos-kdl.inc b/includes-ros1/orocos-kinematics-dynamics/orocos-kdl.inc
index 8572c3d..faf2ccf 100644
--- a/includes-ros1/orocos-kinematics-dynamics/orocos-kdl.inc
+++ b/includes-ros1/orocos-kinematics-dynamics/orocos-kdl.inc
@@ -2,6 +2,13 @@
 
 inherit ros-insane
 
+# Under morty, this line in manifest.xml: <cpp cflags="-I${prefix}/install_dir/include `pkg-config --cflags eigen3`" .../>
+# generates an absolute path for Cflags in *.pc . Convert it to ${includedir}.
+do_install_append() {
+    # Don't write ${include}, as bitbake will expand it.
+    sed -i -e '/^Cflags:/ s@-I/.*/usr/include@-I$\{includedir}@g' ${D}${libdir}/pkgconfig/*.pc
+}
+
 # The cmake files aren't in their own "cmake" subdirectory.
 FILES_${PN}-dev_prepend = " \
     ${datadir}/${ROS_BPN}/*.cmake \