diff --git a/ChangeLog b/ChangeLog
index 1a86d93fa..d73d543dc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,6 @@
+	* Fixed bug #848475 -- bad error message from regexp-expecting
+	commands.
+	
 	* Stopped listing the plugin dispatcher command in the list of
 	commands for that plugin.
 	
diff --git a/src/utils.py b/src/utils.py
index 5b7a6765c..e71396c12 100755
--- a/src/utils.py
+++ b/src/utils.py
@@ -209,7 +209,10 @@ def perlReToPythonRe(s):
     """Converts a string representation of a Perl regular expression (i.e.,
     m/^foo$/i or /foo|bar/) to a Python regular expression.
     """
-    (kind, regexp, flags) = nonEscapedSlashes.split(s)
+    try:
+        (kind, regexp, flags) = nonEscapedSlashes.split(s)
+    except ValueError: # Unpack list of wrong size.
+        raise ValueError, 'Must be of the form m/.../ or /.../'
     regexp = regexp.replace('\\/', '/')
     if kind not in ('', 'm'):
         raise ValueError, 'Invalid kind: must be in ("", "m")'
@@ -229,7 +232,10 @@ def perlReToReplacer(s):
     s/foo/bar/g or s/foo/bar/i) to a Python function doing the equivalent
     replacement.
     """
-    (kind, regexp, replace, flags) = nonEscapedSlashes.split(s)
+    try:
+        (kind, regexp, replace, flags) = nonEscapedSlashes.split(s)
+    except ValueError: # Unpack list of wrong size.
+        raise ValueError, 'Must be of the form s/.../.../'
     replace = replace.replace('\\/', '/')
     if kind != 's':
         raise ValueError, 'Invalid kind: must be "s"'
diff --git a/test/test_Utilities.py b/test/test_Utilities.py
index 0fc602d77..1cd9c6bc9 100644
--- a/test/test_Utilities.py
+++ b/test/test_Utilities.py
@@ -73,4 +73,7 @@ class UtilitiesTestCase(PluginTestCase, PluginDocumentation):
         self.assertNotRegexp('re m/foo/ bar', 'has no attribute')
         self.assertResponse('re m/a\S+y/ "the bot angryman is hairy"','angry')
 
+    def testReNoEscapingUnpackListOfWrongSize(self):
+        self.assertNotRegexp('re foo bar baz', 'unpack list of wrong size')
+
 # vim:set shiftwidth=4 tabstop=8 expandtab textwidth=78: