diff --git a/src/org/fdroid/fdroid/DB.java b/src/org/fdroid/fdroid/DB.java
index 75b27efdc..73236124e 100644
--- a/src/org/fdroid/fdroid/DB.java
+++ b/src/org/fdroid/fdroid/DB.java
@@ -465,6 +465,8 @@ public class DB {
 
     public static String calcFingerprint(String pubkey) {
         String ret = null;
+        if (pubkey == null)
+            return null;
         try {
             // keytool -list -v gives you the SHA-256 fingerprint
             MessageDigest digest = MessageDigest.getInstance("SHA-256");
@@ -1410,7 +1412,7 @@ public class DB {
         String calcedFingerprint = DB.calcFingerprint(pubkey);
         if (fingerprint == null) {
             fingerprint = calcedFingerprint;
-        } else {
+        } else if (calcedFingerprint != null) {
             fingerprint = fingerprint.toUpperCase();
             if (!fingerprint.equals(calcedFingerprint)) {
                 throw new SecurityException("Given fingerprint does not match calculated one! ("