diff --git a/services/lib/docker/build_sources.sh b/services/lib/docker/build_sources.sh
index 73e109049..51b1cfd32 100755
--- a/services/lib/docker/build_sources.sh
+++ b/services/lib/docker/build_sources.sh
@@ -1,20 +1,20 @@
 #!/usr/bin/env bash
 
 set -e
 
 NPROC=0
 
 NPROC=$(nproc 2> /dev/null || echo 1)
 if [[ $NPROC -eq 1 ]]; then
   NPROC=$(sysctl -n hw.physicalcpu 2> /dev/null || echo 1)
 fi
 
 echo "building the server (nproc=$NPROC)..."
 
 pushd cmake/build
 cmake ../..
-make -j $NPROC
+make -j "$NPROC"
 
 popd
 
 echo "success - server built"