diff --git a/CHANGELOG b/CHANGELOG
index 72a77a2f2..6346d7c41 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -19,6 +19,7 @@ CHANGELOG Roundcube Webmail
 - Fix bug where multi-folder search didn't work for unsubscribed INBOX (#5259)
 - Fix bug where "no body" alert could be displayed when sending mailvelope email
 - Enigma: Fix keys import from inside of an encrypted message (#5285)
+- Enigma: Fix malformed signed messages with force_7bit=true (#5292)
 - Fix searching by email address in contacts with multiple addresses (#5291)
 - Fix handling of --delete argument in moduserprefs.sh script (#5296)
 
diff --git a/plugins/enigma/composer.json b/plugins/enigma/composer.json
index 244ba05d4..f9a9195b2 100644
--- a/plugins/enigma/composer.json
+++ b/plugins/enigma/composer.json
@@ -3,7 +3,7 @@
     "type": "roundcube-plugin",
     "description": "PGP Encryption for Roundcube",
     "license": "GPLv3+",
-    "version": "0.5",
+    "version": "0.6",
     "authors": [
         {
             "name": "Aleksander Machniak",
diff --git a/plugins/enigma/lib/enigma_mime_message.php b/plugins/enigma/lib/enigma_mime_message.php
index a9b5536b7..ea37463ad 100644
--- a/plugins/enigma/lib/enigma_mime_message.php
+++ b/plugins/enigma/lib/enigma_mime_message.php
@@ -126,7 +126,9 @@ class enigma_mime_message extends Mail_mime
         $_headers = $this->message->headers();
         $headers  = array();
 
-        if ($_headers['Content-Transfer-Encoding']) {
+        if ($_headers['Content-Transfer-Encoding']
+            && stripos($_headers['Content-Type'], 'multipart') === false
+        ) {
             $headers[] = 'Content-Transfer-Encoding: ' . $_headers['Content-Transfer-Encoding'];
         }
         $headers[] = 'Content-Type: ' . $_headers['Content-Type'];
@@ -142,8 +144,10 @@ class enigma_mime_message extends Mail_mime
     public function addPGPSignature($body)
     {
         $this->signature = $body;
+
         // Reset Content-Type to be overwritten with valid boundary
         unset($this->headers['Content-Type']);
+        unset($this->headers['Content-Transfer-Encoding']);
     }
 
     /**
@@ -154,8 +158,10 @@ class enigma_mime_message extends Mail_mime
     public function setPGPEncryptedBody($body)
     {
         $this->encrypted = $body;
+
         // Reset Content-Type to be overwritten with valid boundary
         unset($this->headers['Content-Type']);
+        unset($this->headers['Content-Transfer-Encoding']);
     }
 
     /**
@@ -193,7 +199,9 @@ class enigma_mime_message extends Mail_mime
                 $headers = $this->message->headers();
                 $params  = array('content_type' => $headers['Content-Type']);
 
-                if ($headers['Content-Transfer-Encoding']) {
+                if ($headers['Content-Transfer-Encoding']
+                    && stripos($headers['Content-Type'], 'multipart') === false
+                ) {
                     $params['encoding'] = $headers['Content-Transfer-Encoding'];
                 }
 
@@ -243,18 +251,24 @@ class enigma_mime_message extends Mail_mime
         if ($filename) {
             // Append mimePart message headers and body into file
             $headers = $message->encodeToFile($filename, $boundary, $skip_head);
+
             if ($this->isError($headers)) {
                 return $headers;
             }
+
             $this->headers = array_merge($this->headers, $headers);
-            return null;
+
+            return;
         }
         else {
             $output = $message->encode($boundary, $skip_head);
+
             if ($this->isError($output)) {
                 return $output;
             }
+
             $this->headers = array_merge($this->headers, $output['headers']);
+
             return $output['body'];
         }
     }
diff --git a/plugins/enigma/lib/enigma_ui.php b/plugins/enigma/lib/enigma_ui.php
index bb0b03012..3fa0f82e3 100644
--- a/plugins/enigma/lib/enigma_ui.php
+++ b/plugins/enigma/lib/enigma_ui.php
@@ -968,19 +968,19 @@ class enigma_ui
         }
 
         if (!$savedraft && $pubkey_enable) {
-            $this->enigma->load_engine();
-            $this->enigma->engine->attach_public_key($p['message']);
+            $engine = $this->enigma->load_engine();
+            $engine->attach_public_key($p['message']);
         }
 
         if (!$savedraft && $sign_enable) {
-            $this->enigma->load_engine();
-            $status = $this->enigma->engine->sign_message($p['message']);
+            $engine = $this->enigma->load_engine();
+            $status = $engine->sign_message($p['message']);
             $mode   = 'sign';
         }
 
         if ((!$status instanceof enigma_error) && $encrypt_enable) {
-            $this->enigma->load_engine();
-            $status = $this->enigma->engine->encrypt_message($p['message'], null, $savedraft);
+            $engine = $this->enigma->load_engine();
+            $status = $engine->encrypt_message($p['message'], null, $savedraft);
             $mode   = 'encrypt';
         }