iverilog error in caravel functional sim. What is it telling me?

../../../../rtl/caravel.v:273: warning: input port clock is coerced to inout.
ivl: vvp_scope.c:753: draw_delay: Assertion `ivl_expr_type(fall_exp) == IVL_EX_SIGNAL' failed.
sh: line 1: 11980 Done                    /usr/lib/x86_64-linux-gnu/ivl/ivlpp -L -F"/tmp/ivrlg25352edf3" -f"/tmp/ivrlg5352edf3" -p"/tmp/ivrli5352edf3"
     11981 Aborted                 | /usr/lib/x86_64-linux-gnu/ivl/ivl -C"/tmp/ivrlh5352edf3" -C"/usr/lib/x86_64-linux-gnu/ivl/vvp.conf" -- -
Makefile:38: recipe for target 'la_test1.vvp' failed
make: *** [la_test1.vvp] Error 134
rm la_test1.vvp