diff --git a/pom.xml b/pom.xml
index 93f05ba..6466062 100644
--- a/pom.xml
+++ b/pom.xml
@@ -159,9 +159,10 @@
         </dependency>
         <!-- https://mvnrepository.com/artifact/net.openhft/chronicle-map -->
         <dependency>
-            <groupId>org.ehcache</groupId>
-            <artifactId>ehcache</artifactId>
-            <version>3.8.1</version>
+            <scope>compile</scope>
+            <groupId>net.openhft</groupId>
+            <artifactId>chronicle-map</artifactId>
+            <version>3.17.8</version>
         </dependency>
     </dependencies>
 </project>
\ No newline at end of file
diff --git a/src/main/java/org/ids_mannheim/TotalNGram.java b/src/main/java/org/ids_mannheim/TotalNGram.java
index 2f691f2..5c405eb 100644
--- a/src/main/java/org/ids_mannheim/TotalNGram.java
+++ b/src/main/java/org/ids_mannheim/TotalNGram.java
@@ -19,6 +19,8 @@
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
+import net.openhft.chronicle.map.*;
+import shaded.org.ops4j.io.FileUtils;
 
 @CommandLine.Command(mixinStandardHelpOptions = true,
         name = "totalngram", description = "add ngram counts from KorAP-XML or CoNLL-U files")
@@ -129,7 +131,13 @@
                     Utils.newExtension(tmpdir + "/" + new File(output_fillename).getName(),
                             "cm"), true);
             logger.info("Creating ChronicleMap with "+estimated_entries+ " entries");
-            map = new org.ehcache.impl.internal.concurrent.ConcurrentHashMap();
+            map = ChronicleMap
+                    .of(String.class, FoldedEntry.class)
+                    .name("ngrams-map")
+                    .averageKey("Amsterdam".repeat(FOLDS))
+                    .averageValue(new FoldedEntry())
+                    .entries(estimated_entries)
+                    .recoverPersistedTo(persisted_map, false);
         } else {
             map = new ConcurrentHashMap();
         }
@@ -156,15 +164,16 @@
         etaPrinter.finish();
         logger.info("Sorting and writing frequency table.");
         System.err.println("Sorting and writing frequency table.");
-        map.entrySet().parallelStream()
-                .forEachOrdered(entry -> output_stream.println(entry.getKey() + entry.getValue().toString()));
+        map.entrySet().stream()
+                .sorted(new FreqListEntryComparator<>())
+                .forEach(entry -> output_stream.println(entry.getKey() + entry.getValue().toString()));
         logger.info("Calculating column sums.");
-        if (map instanceof ConcurrentHashMap || map instanceof org.ehcache.impl.internal.concurrent.ConcurrentHashMap) {
+        if (map instanceof ConcurrentHashMap) {
             logger.info("Calculating column sums.");
             System.err.println("Calculating column sums.");
-            IntStream.rangeClosed(1, FOLDS).parallel()
-                    .forEachOrdered(i -> output_stream.print("\t" + Long.toUnsignedString(map.values()
-                            .parallelStream().mapToLong(e -> Integer.toUnsignedLong(e.count.get(i))).sum())));
+            IntStream.rangeClosed(1, FOLDS)
+                    .forEach(i -> output_stream.print("\t" + Long.toUnsignedString(map.values()
+                            .stream().mapToLong(e -> Integer.toUnsignedLong(e.count.get(i))).sum())));
             output_stream.println("\t" + Long.toUnsignedString(map.values().stream().mapToLong(e -> Integer.toUnsignedLong(e.count.get(0))).sum()));
         } else {
             logger.info("Skip column sums calculation which is too slow with persisted hash maps.");
diff --git a/src/main/java/org/ids_mannheim/Worker.java b/src/main/java/org/ids_mannheim/Worker.java
index 49f1944..6b123f2 100644
--- a/src/main/java/org/ids_mannheim/Worker.java
+++ b/src/main/java/org/ids_mannheim/Worker.java
@@ -1,6 +1,7 @@
 package org.ids_mannheim;
 
-import java.io.BufferedReader;
+import net.openhft.chronicle.map.ChronicleMap;
+
 import java.io.BufferedReader;
 import java.io.File;
 import java.io.IOException;