diff --git a/lib/galaxy/datatypes/data.py b/lib/galaxy/datatypes/data.py
index afa4f351b1e..ee19a938c69 100644
--- a/lib/galaxy/datatypes/data.py
+++ b/lib/galaxy/datatypes/data.py
@@ -407,7 +407,15 @@ class Text( Data ):
                 else:
                     # Number of lines is not known ( this should not happen ), and auto-detect is
                     # needed to set metadata
-                    dataset.blurb = "? lines"
+                    # This can happen when the file is larger than max_optional_metadata_filesize.
+                    # Perform a rough estimate by extrapolating number of lines from a small read.
+                    sample_size = min(self.max_optional_metadata_filesize, 1048576)
+                    dataset_fh = open( dataset.file_name )
+                    dataset_read = dataset_fh.read(sample_size)
+                    dataset_fh.close()
+                    sample_lines = dataset_read.count('\n')
+                    est_lines = int(sample_lines * (dataset.get_size() / float(sample_size)))
+                    dataset.blurb = "~%s lines" % util.commaify(str(est_lines))
             else:
                 dataset.blurb = "%s lines" % util.commaify( str( line_count ) )
         else: