diff --git a/common/src/main/java/ctbrec/Version.java b/common/src/main/java/ctbrec/Version.java
index a84e9e6d..203a1523 100644
--- a/common/src/main/java/ctbrec/Version.java
+++ b/common/src/main/java/ctbrec/Version.java
@@ -1,5 +1,6 @@
 package ctbrec;
 
+import java.util.Objects;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -10,14 +11,15 @@ public class Version implements Comparable<Version> {
     String designator = "";
 
     public static Version of(String s) {
+        Objects.requireNonNull(s, "Version string cannot be null");
         Pattern p = Pattern.compile("(\\d+)\\.(\\d+)\\.(\\d+)(?:-(.+))?");
         Matcher m = p.matcher(s);
-        if(m.matches()) {
+        if (m.matches()) {
             Version v = new Version();
             v.major = Integer.parseInt(m.group(1));
             v.minor = Integer.parseInt(m.group(2));
             v.revision = Integer.parseInt(m.group(3));
-            if(m.group(4) != null) {
+            if (m.group(4) != null) {
                 v.designator = m.group(4);
             }
             return v;