diff --git a/libse/SubtitleFormats/MacSub.cs b/libse/SubtitleFormats/MacSub.cs
index e329b5419..2d2d47fdd 100644
--- a/libse/SubtitleFormats/MacSub.cs
+++ b/libse/SubtitleFormats/MacSub.cs
@@ -55,7 +55,7 @@ namespace Nikse.SubtitleEdit.Core.SubtitleFormats
             _errorCount = 0;
             char[] trimChar = { '/' };
             var p = new Paragraph();
-            for (int i = 0; i < lines.Count; i++)
+            for (int i = 0, lineNumber = 1; i < lines.Count; i++)
             {
                 string line = lines[i].Trim();
                 string nextLine = null;
@@ -86,7 +86,7 @@ namespace Nikse.SubtitleEdit.Core.SubtitleFormats
                             if ((nextLine == null) || (nextLine.Length > 0 && nextLine[0] == '/'))
                             {
                                 expecting = Expecting.EndFrame;
-                                p.Number = i;
+                                p.Number = lineNumber++;
                             }
                             break;