diff --git a/Lib/logging/__init__.py b/Lib/logging/__init__.py
index 6baf9b4..2f081a0 100644
--- a/Lib/logging/__init__.py
+++ b/Lib/logging/__init__.py
@@ -1211,7 +1211,7 @@
             if filename == _srcfile:
                 f = f.f_back
                 continue
-            rv = (filename, f.f_lineno, co.co_name)
+            rv = (co.co_filename, f.f_lineno, co.co_name)
             break
         return rv
 
diff --git a/Misc/NEWS b/Misc/NEWS
index b8bdd9c..613afd9 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -48,6 +48,8 @@
 Library
 -------
 
+- Issue #9948: Fixed problem of losing filename case information.
+
 - Issue #9437: Fix building C extensions with non-default LDFLAGS.
 
 - Issue #9759: GzipFile now raises ValueError when an operation is attempted