diff --git a/ci.hocon b/ci.hocon
index 19a2e55828f1e73fac9f2970863858c2581c98ff..d5cf84ac387ebac120d66ff1cb59f15876a52eb7 100644
--- a/ci.hocon
+++ b/ci.hocon
@@ -58,7 +58,7 @@ pkgtest: ${common} ${java8Downloads} {
     ["git", "clone", "--depth", "1", ${repoBase}"gnur.git",  "../gnur"]
   ]
   run : [
-    ["mx", "-v", "--dynamicimport", "gnur", "build"]
+    ["mx", "-v", "--dynamicimport", "gnur", "build", "--serial"]
     ["mx", "--dynamicimport", "gnur", "pkgtest", "--print-ok-installs", "--ok-only"]
   ]
 }