diff --git a/scripts/install-mimic.sh b/scripts/install-mimic.sh
index 86ffc4a6ab..1d13545a28 100755
--- a/scripts/install-mimic.sh
+++ b/scripts/install-mimic.sh
@@ -18,7 +18,7 @@
 set -Ee
 
 MIMIC_DIR=mimic
-CORES=$1
+CORES=${1:-1}
 MIMIC_VERSION=1.2.0.2
 
 # for ubuntu precise in travis, that does not provide pkg-config: