diff --git a/src/omemo/omemo.c b/src/omemo/omemo.c
index 9dac4d76..e3a652b1 100644
--- a/src/omemo/omemo.c
+++ b/src/omemo/omemo.c
@@ -1147,6 +1147,7 @@ omemo_on_message_recv(const char* const from_jid, uint32_t sid,
 
     if (payload == NULL) {
         signal_buffer_free(plaintext_key);
+        *error = OMEMO_ERR_KEY_TRANSPORT;
         return NULL;
     }
 
diff --git a/src/xmpp/message.c b/src/xmpp/message.c
index 09f90ba9..76179efc 100644
--- a/src/xmpp/message.c
+++ b/src/xmpp/message.c
@@ -1089,25 +1089,7 @@ _handle_groupchat(xmpp_stanza_t* const stanza)
     if (message->omemo_err != OMEMO_ERR_NONE) {
         message->enc = PROF_MSG_ENC_OMEMO;
         if (message->plain == NULL) {
-            switch (message->omemo_err) {
-            case OMEMO_ERR_NO_KEY:
-                message->plain = g_strdup("OMEMO message received but no key for this device found.");
-                break;
-            case OMEMO_ERR_NOT_TRUSTED:
-                message->plain = g_strdup("OMEMO message received but sender identity is untrusted.");
-                break;
-            case OMEMO_ERR_NO_SESSION:
-                message->plain = g_strdup("OMEMO message received but no session found. Try '/omemo start'.");
-                break;
-            case OMEMO_ERR_DECRYPT_FAILED:
-                message->plain = g_strdup("OMEMO message received but decryption failed.");
-                break;
-            case OMEMO_ERR_KEY_TRANSPORT:
-                break;
-            default:
-                message->plain = g_strdup("OMEMO message received but could not be decrypted.");
-                break;
-            }
+            message->plain = omemo_error_to_string(message->omemo_err);
         }
     } else if (message->plain != NULL) {
         message->enc = PROF_MSG_ENC_OMEMO;
@@ -1272,25 +1254,7 @@ _handle_muc_private_message(xmpp_stanza_t* const stanza)
     if (message->omemo_err != OMEMO_ERR_NONE) {
         message->enc = PROF_MSG_ENC_OMEMO;
         if (message->plain == NULL) {
-            switch (message->omemo_err) {
-            case OMEMO_ERR_NO_KEY:
-                message->plain = g_strdup("OMEMO message received but no key for this device found.");
-                break;
-            case OMEMO_ERR_NOT_TRUSTED:
-                message->plain = g_strdup("OMEMO message received but sender identity is untrusted.");
-                break;
-            case OMEMO_ERR_NO_SESSION:
-                message->plain = g_strdup("OMEMO message received but no session found. Try '/omemo start'.");
-                break;
-            case OMEMO_ERR_DECRYPT_FAILED:
-                message->plain = g_strdup("OMEMO message received but decryption failed.");
-                break;
-            case OMEMO_ERR_KEY_TRANSPORT:
-                break;
-            default:
-                message->plain = g_strdup("OMEMO message received but could not be decrypted.");
-                break;
-            }
+            message->plain = omemo_error_to_string(message->omemo_err);
         }
     } else if (message->plain != NULL) {
         message->enc = PROF_MSG_ENC_OMEMO;
@@ -1462,25 +1426,7 @@ _handle_chat(xmpp_stanza_t* const stanza, gboolean is_mam, gboolean is_carbon, c
     if (message->omemo_err != OMEMO_ERR_NONE) {
         message->enc = PROF_MSG_ENC_OMEMO;
         if (message->plain == NULL) {
-            switch (message->omemo_err) {
-            case OMEMO_ERR_NO_KEY:
-                message->plain = g_strdup("OMEMO message received but no key for this device found.");
-                break;
-            case OMEMO_ERR_NOT_TRUSTED:
-                message->plain = g_strdup("OMEMO message received but sender identity is untrusted.");
-                break;
-            case OMEMO_ERR_NO_SESSION:
-                message->plain = g_strdup("OMEMO message received but no session found. Try '/omemo start'.");
-                break;
-            case OMEMO_ERR_DECRYPT_FAILED:
-                message->plain = g_strdup("OMEMO message received but decryption failed.");
-                break;
-            case OMEMO_ERR_KEY_TRANSPORT:
-                break;
-            default:
-                message->plain = g_strdup("OMEMO message received but could not be decrypted.");
-                break;
-            }
+            message->plain = omemo_error_to_string(message->omemo_err);
         }
     } else if (message->plain != NULL) {
         message->enc = PROF_MSG_ENC_OMEMO;
diff --git a/src/xmpp/omemo.c b/src/xmpp/omemo.c
index 9238f493..cef09dde 100644
--- a/src/xmpp/omemo.c
+++ b/src/xmpp/omemo.c
@@ -421,10 +421,6 @@ omemo_receive_message(xmpp_stanza_t* const stanza, gboolean* trusted, omemo_erro
                                       keys, payload_raw, payload_len,
                                       g_strcmp0(type, STANZA_TYPE_GROUPCHAT) == 0, trusted, error);
 
-    if (plaintext == NULL && *error == OMEMO_ERR_NONE && payload == NULL) {
-        *error = OMEMO_ERR_KEY_TRANSPORT;
-    }
-
     if (keys) {
         g_list_free_full(keys, (GDestroyNotify)omemo_key_free);
     }
@@ -707,3 +703,24 @@ _omemo_bundle_publish_configure_result(xmpp_stanza_t* const stanza, void* const
 
     return 0;
 }
+
+char*
+omemo_error_to_string(omemo_error_t error)
+{
+    switch (error) {
+    case OMEMO_ERR_NO_KEY:
+        return g_strdup("OMEMO message received but no key for this device found.");
+    case OMEMO_ERR_NOT_TRUSTED:
+        return g_strdup("OMEMO message received but sender identity is untrusted.");
+    case OMEMO_ERR_NO_SESSION:
+        return g_strdup("OMEMO message received but no session found. Try '/omemo start'.");
+    case OMEMO_ERR_DECRYPT_FAILED:
+        return g_strdup("OMEMO message received but decryption failed.");
+    case OMEMO_ERR_KEY_TRANSPORT:
+        return NULL;
+    case OMEMO_ERR_NONE:
+        return NULL;
+    default:
+        return g_strdup("OMEMO message received but could not be decrypted.");
+    }
+}
diff --git a/src/xmpp/omemo.h b/src/xmpp/omemo.h
index ff6d648b..772bd186 100644
--- a/src/xmpp/omemo.h
+++ b/src/xmpp/omemo.h
@@ -20,3 +20,4 @@ void omemo_bundle_request(const char* const jid, uint32_t device_id, ProfIqCallb
 int omemo_start_device_session_handle_bundle(xmpp_stanza_t* const stanza, void* const userdata);
 
 char* omemo_receive_message(xmpp_stanza_t* const stanza, gboolean* trusted, omemo_error_t* error) __attribute__((nonnull(2, 3)));
+char* omemo_error_to_string(omemo_error_t error);