diff --git a/src/main/java/eu/siacs/conversations/utils/CryptoHelper.java b/src/main/java/eu/siacs/conversations/utils/CryptoHelper.java
index 466bc4098..2dec203d9 100644
--- a/src/main/java/eu/siacs/conversations/utils/CryptoHelper.java
+++ b/src/main/java/eu/siacs/conversations/utils/CryptoHelper.java
@@ -91,7 +91,9 @@ public final class CryptoHelper {
 	}
 
 	public static String prettifyFingerprint(String fingerprint) {
-		if (fingerprint.length() < 40) {
+		if (fingerprint==null) {
+			return "";
+		} else if (fingerprint.length() < 40) {
 			return fingerprint;
 		}
 		StringBuilder builder = new StringBuilder(fingerprint);