diff --git a/Lib/logging/__init__.py b/Lib/logging/__init__.py
index 112286b..b9cea3f 100644
--- a/Lib/logging/__init__.py
+++ b/Lib/logging/__init__.py
@@ -1174,7 +1174,7 @@
             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 7a8a8f9..57cc97f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -92,6 +92,8 @@
 Library
 -------
 
+- Issue #9948: Fixed problem of losing filename case information.
+
 - Issue #9437: Fix building C extensions with non-default LDFLAGS.
 
 - Issue #4661: email can now parse bytes input and generate either converted