diff --git a/ci/build_hermes.sh b/ci/build_hermes.sh
index 223e7d4f5..63637df26 100755
--- a/ci/build_hermes.sh
+++ b/ci/build_hermes.sh
@@ -72,7 +72,7 @@ ctest -VV
 
 # Run make install unit test
 cd /hermes/test/unit/external
-mkdir build
+mkdir -p build
 cd build
 cmake ../
 make -j4