diff --git a/aqt/importing.py b/aqt/importing.py
index 2ada664af..27787ec4c 100644
--- a/aqt/importing.py
+++ b/aqt/importing.py
@@ -112,6 +112,11 @@ you can enter it here. Use \\t to represent tab."""),
                 self, help="importing") or "\t"
         str = str.replace("\\t", "\t")
         str = str.encode("ascii")
+        if len(str) > 1:
+            showWarning(_(
+                "Multi-character separators are not supported. "
+                "Please enter one character only."))
+            return
         self.hideMapping()
         def updateDelim():
             self.importer.delimiter = str
@@ -140,7 +145,7 @@ you can enter it here. Use \\t to represent tab."""),
             d = repr(d)
         txt = _("Fields separated by: %s") % d
         self.frm.autoDetect.setText(txt)
-        
+
     def accept(self):
         self.importer.mapping = self.mapping
         if not self.importer.mappingOk():