diff --git a/dv/uvm/core_ibex/yaml/rtl_simulation.yaml b/dv/uvm/core_ibex/yaml/rtl_simulation.yaml
index 6d3d76f3..a973e7ad 100644
--- a/dv/uvm/core_ibex/yaml/rtl_simulation.yaml
+++ b/dv/uvm/core_ibex/yaml/rtl_simulation.yaml
@@ -33,7 +33,6 @@
           -timescale=1ns/10ps
           -licqueue
           -LDFLAGS '-Wl,--no-as-needed'
-          -CFLAGS '--std=c99 -fno-extended-identifiers'
           -Mdir=<tb_dir>/vcs_simv.csrc
           -o <tb_dir>/vcs_simv
           -debug_access+pp