diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index f8ecbc8..042feb6 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -92,8 +92,8 @@
     - start_section building_index "Building index"
     - touch target/*.zip # ignore timestamps in make
     - sleep 1
-    - touch target/*.ud.zip
-    - make -j $(nproc) target/dnb.index.tar.xz
+    - touch target/*.*.zip
+    - MAX_THREADS=2 make -j $(nproc) target/dnb.index.tar.xz
     - end_section building_krill
   artifacts:
     paths:
diff --git a/Makefile b/Makefile
index eb0aca7..6f1c77f 100644
--- a/Makefile
+++ b/Makefile
@@ -4,6 +4,7 @@
 DEPLOY_HOST ?= compute.ids-mannheim.de
 DEPLOY_USER ?= korap
 DEPLOY_PATH ?= /export/netapp/korap4dnb
+MAX_THREADS ?= $(shell nproc)
 
 .PHONY: all clean test krill index deploy server-log server-status
 
@@ -54,7 +55,7 @@
 	wget -O $@  https://corpora.ids-mannheim.de/tools/$@
 
 %.marmot-malt.zip: %.zip models/de.marmot models/german.mco
-	$(KORAPXML2CONLLU) -t marmot:models/de.marmot -P malt:models/german.mco $< | tee $(TARGET_DIR)/dnb.marmot-malt.conllu | conllu2korapxml > $@
+	$(KORAPXML2CONLLU) -T $(MAX_THREADS) -t marmot:models/de.marmot -P malt:models/german.mco $< | tee $(TARGET_DIR)/dnb.marmot-malt.conllu | conllu2korapxml > $@
 
 %.ud.zip: %.zip
 	$(KORAPXML2CONLLU) $< | pv | ./scripts/udpipe2 | conllu2korapxml > $@