diff --git a/src/omemo/omemo.c b/src/omemo/omemo.c
index f31acb1d..38157336 100644
--- a/src/omemo/omemo.c
+++ b/src/omemo/omemo.c
@@ -1283,8 +1283,12 @@ omemo_is_trusted_identity(const char* const jid, const char* const fingerprint)
         .device_id = GPOINTER_TO_UINT(device_id),
     };
 
-    size_t fingerprint_len;
+    size_t fingerprint_len = 0;
     unsigned char* fingerprint_raw = _omemo_fingerprint_decode(fingerprint, &fingerprint_len);
+    if (!fingerprint_raw) {
+        log_error("[OMEMO] omemo_is_trusted_identity: failed to decode fingerprint for %s", jid);
+        return FALSE;
+    }
     unsigned char djb_type[] = { '\x05' };
     signal_buffer* buffer = signal_buffer_create(djb_type, 1);
     buffer = signal_buffer_append(buffer, fingerprint_raw, fingerprint_len);
@@ -1468,6 +1472,10 @@ _omemo_fingerprint(ec_public_key* identity, gboolean formatted)
 static unsigned char*
 _omemo_fingerprint_decode(const char* const fingerprint, size_t* len)
 {
+    if (!fingerprint) {
+        *len = 0;
+        return NULL;
+    }
     unsigned char* output = malloc(strlen(fingerprint) / 2 + 1);
     if (!output) {
         *len = 0;
@@ -1534,6 +1542,11 @@ omemo_trust(const char* const jid, const char* const fingerprint_formatted)
     };
 
     unsigned char* fingerprint_raw = _omemo_fingerprint_decode(fingerprint_formatted, &len);
+    if (!fingerprint_raw) {
+        log_error("[OMEMO] omemo_trust: failed to decode fingerprint for %s", jid);
+        cons_show_error("Failed to trust device: could not decode fingerprint.");
+        return;
+    }
     unsigned char djb_type[] = { '\x05' };
     signal_buffer* buffer = signal_buffer_create(djb_type, 1);
     buffer = signal_buffer_append(buffer, fingerprint_raw, len);
@@ -1551,8 +1564,10 @@ omemo_untrust(const char* const jid, const char* const fingerprint_formatted)
 {
     size_t len;
     unsigned char* identity = _omemo_fingerprint_decode(fingerprint_formatted, &len);
-    if (!identity)
+    if (!identity) {
+        log_error("[OMEMO] omemo_untrust: failed to decode fingerprint for %s", jid);
         return;
+    }
 
     GHashTableIter iter;
     gpointer key, value;