diff --git a/mms-lib/src/mms_attachment.c b/mms-lib/src/mms_attachment.c
index 320fb52..0fc8233 100644
--- a/mms-lib/src/mms_attachment.c
+++ b/mms-lib/src/mms_attachment.c
@@ -107,6 +107,7 @@ mms_attachment_get_path(
 #endif
 }
 
+static
 gboolean
 mms_attachment_write_smil(
     FILE* f,
@@ -164,6 +165,44 @@ mms_attachment_write_smil(
     return FALSE;
 }
 
+char*
+mms_attachment_guess_content_type(
+    const char* path)
+{
+    char* content_type = NULL;
+    const char* detected_type = NULL;
+
+#ifdef HAVE_MAGIC
+    /* Use magic to determine mime type */
+    magic_t magic = magic_open(MAGIC_MIME_TYPE);
+    if (magic) {
+        if (magic_load(magic, NULL) == 0) {
+            detected_type = magic_file(magic, path);
+        }
+    }
+#endif
+
+    /* Magic detects SMIL as text/html */
+    if ((!detected_type ||
+         g_str_has_prefix(detected_type, "text/")) &&
+         mms_file_is_smil(path)) {
+        detected_type = SMIL_CONTENT_TYPE;
+    }
+
+    if (!detected_type) {
+        MMS_WARN("No mime type for %s", path);
+        detected_type = MMS_ATTACHMENT_DEFAULT_TYPE;
+    }
+
+    content_type = g_strdup(detected_type);
+
+#ifdef HAVE_MAGIC
+    if (magic) magic_close(magic);
+#endif
+
+    return content_type;
+}
+
 MMSAttachment*
 mms_attachment_new_smil(
     const MMSConfig* config,
@@ -214,7 +253,7 @@ mms_attachment_new(
             GType type;
             MMSAttachment* at;
 
-            if (info->content_type) {
+            if (info->content_type && info->content_type[0]) {
                 char** ct = mms_parse_http_content_type(info->content_type);
                 if (ct) {
                     content_type = mms_unparse_http_content_type(ct);
@@ -226,33 +265,11 @@ mms_attachment_new(
             }
 
             if (!content_type) {
-                /* Use magic to determine mime type */
+                char* detected_type = mms_attachment_guess_content_type(path);
                 const char* default_charset = "utf-8";
-                const char* detected_type = NULL;
                 const char* charset = NULL;
                 const char* ct[4];
-                int n;
-
-#ifdef HAVE_MAGIC
-                magic_t magic = magic_open(MAGIC_MIME_TYPE);
-                if (magic) {
-                    if (magic_load(magic, NULL) == 0) {
-                        detected_type = magic_file(magic, path);
-                    }
-                }
-#endif
-
-                /* Magic detects SMIL as text/html */
-                if ((!detected_type ||
-                     g_str_has_prefix(detected_type, "text/")) &&
-                     mms_file_is_smil(path)) {
-                    detected_type = SMIL_CONTENT_TYPE;
-                }
-
-                if (!detected_type) {
-                    MMS_WARN("No mime type for %s", path);
-                    detected_type = MMS_ATTACHMENT_DEFAULT_TYPE;
-                }
+                int n = 0;
 
                 if (!strcmp(detected_type, SMIL_CONTENT_TYPE)) {
                     flags |= MMS_ATTACHMENT_SMIL;
@@ -261,7 +278,6 @@ mms_attachment_new(
                     charset = default_charset;
                 }
 
-                n = 0;
                 ct[n++] = detected_type;
                 if (charset) {
                     ct[n++] = "charset";
@@ -269,10 +285,7 @@ mms_attachment_new(
                 }
                 ct[n++] = NULL;
                 content_type = mms_unparse_http_content_type((char**)ct);
-
-#ifdef HAVE_MAGIC
-                if (magic) magic_close(magic);
-#endif
+                g_free(detected_type);
             }
 
             MMS_DEBUG("%s: %s", path, content_type);
diff --git a/mms-lib/src/mms_attachment.h b/mms-lib/src/mms_attachment.h
index 1dd7833..6451533 100644
--- a/mms-lib/src/mms_attachment.h
+++ b/mms-lib/src/mms_attachment.h
@@ -74,6 +74,10 @@ void
 mms_attachment_reset(
     MMSAttachment* attachment);
 
+char*
+mms_attachment_guess_content_type(
+    const char* path);
+
 gboolean
 mms_attachment_resize(
     MMSAttachment* attachment);
diff --git a/mms-lib/src/mms_task_encode.c b/mms-lib/src/mms_task_encode.c
index 73d046e..4b1f01f 100644
--- a/mms-lib/src/mms_task_encode.c
+++ b/mms-lib/src/mms_task_encode.c
@@ -461,12 +461,22 @@ mms_task_encode_prepare_attachments(
     for (i=0; i<nparts; i++) {
         MMSAttachment* attachment = NULL;
         MMSAttachmentInfo info = parts[i];
-        G_GNUC_BEGIN_IGNORE_DEPRECATIONS
-        char* path = mms_task_encode_generate_path(dir,
+        char* detected_type = NULL;
+        char* path;
+        GFile* src;
+        GFile* dest;
+
+        if (!info.content_type || !info.content_type[0]) {
+            detected_type = mms_attachment_guess_content_type(info.file_name);
+            info.content_type = detected_type;
+        }
+        G_GNUC_BEGIN_IGNORE_DEPRECATIONS;
+        path = mms_task_encode_generate_path(dir,
             g_basename(info.file_name), info.content_type);
-        G_GNUC_END_IGNORE_DEPRECATIONS
-        GFile* src = g_file_new_for_path(info.file_name);
-        GFile* dest = g_file_new_for_path(path);
+        G_GNUC_END_IGNORE_DEPRECATIONS;
+
+        src = g_file_new_for_path(info.file_name);
+        dest = g_file_new_for_path(path);
         if (g_file_copy(src, dest, 0, NULL, NULL, NULL, error)) {
             info.file_name = path;
             attachment = mms_attachment_new(config, &info, error);
@@ -482,6 +492,7 @@ mms_task_encode_prepare_attachments(
         }
         g_object_unref(src);
         g_object_unref(dest);
+        g_free(detected_type);
         g_free(path);
         if (!attachment) break;
     }
diff --git a/mms-lib/test/send/test_send.c b/mms-lib/test/send/test_send.c
index 08c951d..cc7ce96 100644
--- a/mms-lib/test/send/test_send.c
+++ b/mms-lib/test/send/test_send.c
@@ -80,8 +80,8 @@ static const MMSAttachmentInfo test_files_accept [] = {
 
 static const MMSAttachmentInfo test_files_accept_no_ext [] = {
     { "smil", NULL, NULL },
-    { "0001", "image/jpeg", "image1" },
-    { "0001", "image/jpeg", "image2" },
+    { "0001", NULL, "image1" },
+    { "0001", "", "image2" },
     { "test.text", "text/plain;charset=utf-8", "text" }
 };