diff --git a/django/views/debug.py b/django/views/debug.py
index cf0b6b5a0b..717de1eb34 100644
--- a/django/views/debug.py
+++ b/django/views/debug.py
@@ -201,16 +201,15 @@ def _get_lines_from_file(filename, lineno, context_lines, loader=None, module_na
     if source is None:
         return None, [], None, []
 
-    encoding=None
+    encoding = 'ascii'
     for line in source[:2]:
-        # File coding may be specified (and may not be UTF-8). Match
-        # pattern from PEP-263 (http://www.python.org/dev/peps/pep-0263/)
+        # File coding may be specified. Match pattern from PEP-263
+        # (http://www.python.org/dev/peps/pep-0263/)
         match = re.search(r'coding[:=]\s*([-\w.]+)', line)
         if match:
             encoding = match.group(1)
             break
-    if encoding:
-        source = [unicode(sline, encoding) for sline in source]
+    source = [unicode(sline, encoding, 'replace') for sline in source]
 
     lower_bound = max(0, lineno - context_lines)
     upper_bound = lineno + context_lines