diff --git a/ci/configs/default.bash b/ci/configs/default.bash
index 56231228..50c55956 100644
--- a/ci/configs/default.bash
+++ b/ci/configs/default.bash
@@ -1,5 +1,5 @@
 CI_DESC="CI job using default libraries and tools, and running IWYU"
 CI_DIR=build-default
-export CXXFLAGS="-Werror -Wall -Wextra -Wpedantic -Wno-unused-parameter"
+export CXXFLAGS="-Werror -Wall -Wextra -Wpedantic -Wno-unused-parameter -Wextra-semi"
 CMAKE_ARGS=(-DMP_ENABLE_IWYU=ON)
 BUILD_ARGS=(-k)