diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -3897,14 +3897,21 @@ def log(ui, repo, *pats, **opts):
             return
         if df and not df(ctx.date()[0]):
             return
-        if opts['user'] and not [k for k in opts['user']
-                                 if k.lower() in ctx.user().lower()]:
-            return
+
+        lower = encoding.lower
+        if opts.get('user'):
+            luser = lower(ctx.user())
+            for k in [lower(x) for x in opts['user']]:
+                if (k in luser):
+                    break
+            else:
+                return
         if opts.get('keyword'):
-            for k in [kw.lower() for kw in opts['keyword']]:
-                if (k in ctx.user().lower() or
-                    k in ctx.description().lower() or
-                    k in " ".join(ctx.files()).lower()):
+            luser = lower(ctx.user())
+            ldesc = lower(ctx.description())
+            lfiles = lower(" ".join(ctx.files()))
+            for k in [lower(x) for x in opts['keyword']]:
+                if (k in luser or k in ldesc or k in lfiles):
                     break
             else:
                 return
diff --git a/tests/test-log.t b/tests/test-log.t
--- a/tests/test-log.t
+++ b/tests/test-log.t
@@ -1159,3 +1159,56 @@ Diff here should be the same:
   $ hg log --template='{rev}:{node}\n' --hidden
   1:a765632148dc55d38c35c4f247c618701886cb2f
   0:9f758d63dcde62d547ebfb08e1e7ee96535f2b05
+
+clear extensions configuration
+  $ echo '[extensions]' >> $HGRCPATH
+  $ echo "hidden=!" >> $HGRCPATH
+  $ cd ..
+
+test -u/-k for problematic encoding
+# unicode: cp932:
+# u30A2    0x83 0x41(= 'A')
+# u30C2    0x83 0x61(= 'a')
+
+  $ hg init problematicencoding
+  $ cd problematicencoding
+
+  $ python > setup.sh <<EOF
+  > print u'''
+  > echo a > text
+  > hg add text
+  > hg --encoding utf-8 commit -u '\u30A2' -m none
+  > echo b > text
+  > hg --encoding utf-8 commit -u '\u30C2' -m none
+  > echo c > text
+  > hg --encoding utf-8 commit -u none -m '\u30A2'
+  > echo d > text
+  > hg --encoding utf-8 commit -u none -m '\u30C2'
+  > '''.encode('utf-8')
+  > EOF
+  $ sh < setup.sh
+
+test in problematic encoding
+  $ python > test.sh <<EOF
+  > print u'''
+  > hg --encoding cp932 log --template '{rev}\\n' -u '\u30A2'
+  > echo ====
+  > hg --encoding cp932 log --template '{rev}\\n' -u '\u30C2'
+  > echo ====
+  > hg --encoding cp932 log --template '{rev}\\n' -k '\u30A2'
+  > echo ====
+  > hg --encoding cp932 log --template '{rev}\\n' -k '\u30C2'
+  > '''.encode('cp932')
+  > EOF
+  $ sh < test.sh
+  0
+  ====
+  1
+  ====
+  2
+  0
+  ====
+  3
+  1
+
+  $ cd ..