diff --git a/src/IrcClient/IrcClient.cs b/src/IrcClient/IrcClient.cs
index 3d6b7f1..a0e8f86 100644
--- a/src/IrcClient/IrcClient.cs
+++ b/src/IrcClient/IrcClient.cs
@@ -906,9 +906,9 @@ public IrcMessageData MessageParser(string rawline)
             // conform to RFC 2812
             from = linear[0];
             messagecode = linear[1];
-            exclamationpos = from.IndexOf("!");
-            atpos = from.IndexOf("@");
-            colonpos = line.IndexOf(" :");
+            exclamationpos = from.IndexOf("!", StringComparison.Ordinal);
+            atpos = from.IndexOf("@", StringComparison.Ordinal);
+            colonpos = line.IndexOf(" :", StringComparison.Ordinal);
             if (colonpos != -1) {
                 // we want the exact position of ":" not beginning from the space
                 colonpos += 1;