diff --git a/src/Libraries/NRefactory/Project/Src/Lexer/AbstractLexer.cs b/src/Libraries/NRefactory/Project/Src/Lexer/AbstractLexer.cs
index 805d81dd9b..571d22849c 100644
--- a/src/Libraries/NRefactory/Project/Src/Lexer/AbstractLexer.cs
+++ b/src/Libraries/NRefactory/Project/Src/Lexer/AbstractLexer.cs
@@ -48,11 +48,13 @@ namespace ICSharpCode.NRefactory.Parser
 		
 		protected static IEnumerable<string> GetSymbols (string symbols)
 		{
-			foreach (string symbol in symbols.Split (';')) {
-				string s = symbol.Trim ();
-				if (s.Length == 0)
-					continue;
-				yield return s;
+			if (!string.IsNullOrEmpty(symbols)) {
+				foreach (string symbol in symbols.Split (';')) {
+					string s = symbol.Trim ();
+					if (s.Length == 0)
+						continue;
+					yield return s;
+				}
 			}
 		}