diff --git a/mercurial/commands.py b/mercurial/commands.py
index 6470f476d6..fc64c13aa4 100644
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -1092,7 +1092,11 @@ def grep(ui, repo, pattern, *pats, **opts):
     reflags = 0
     if opts['ignore_case']:
         reflags |= re.I
-    regexp = re.compile(pattern, reflags)
+    try:
+        regexp = re.compile(pattern, reflags)
+    except Exception, inst:
+        ui.warn(_("grep: invalid match pattern: %s!\n") % inst)
+        return None
     sep, eol = ':', '\n'
     if opts['print0']:
         sep = eol = '\0'
diff --git a/tests/test-grep b/tests/test-grep
index 92c00fcbe2..5ac3bda274 100755
--- a/tests/test-grep
+++ b/tests/test-grep
@@ -17,6 +17,8 @@ hg commit -m 3 -u eggs -d '3 0'
 head -n 3 port > port1
 mv port1 port
 hg commit -m 4 -u spam -d '4 0'
+echo % pattern error
+hg grep '**test**'
 echo % simple
 hg grep port port
 echo % all
diff --git a/tests/test-grep.out b/tests/test-grep.out
index dd5f5b2c5e..c8ae48b7c3 100644
--- a/tests/test-grep.out
+++ b/tests/test-grep.out
@@ -1,3 +1,5 @@
+% pattern error
+grep: invalid match pattern: nothing to repeat!
 % simple
 port:4:export
 port:4:vaportight