Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.391
diff -u -p -r1.391 form.inc
--- includes/form.inc	3 Nov 2009 05:27:18 -0000	1.391
+++ includes/form.inc	3 Nov 2009 22:47:11 -0000
@@ -1828,8 +1828,8 @@ function form_process_password_confirm($
  */
 function password_confirm_validate($element, &$element_state) {
   $pass1 = trim($element['pass1']['#value']);
-  if (!empty($pass1)) {
-    $pass2 = trim($element['pass2']['#value']);
+  $pass2 = trim($element['pass2']['#value']);
+  if (!empty($pass1) || !empty($pass2)) {
     if (strcmp($pass1, $pass2)) {
       form_error($element, t('The specified passwords do not match.'));
     }
Index: modules/user/user.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/user/user.test,v
retrieving revision 1.66
diff -u -p -r1.66 user.test
--- modules/user/user.test	1 Nov 2009 21:26:44 -0000	1.66
+++ modules/user/user.test	3 Nov 2009 22:47:12 -0000
@@ -53,7 +53,7 @@ class UserRegistrationTestCase extends D
     $edit['pass[pass1]'] = '99999.0';
     $edit['pass[pass2]'] = '99999';
     $this->drupalPost('user/register', $edit, t('Create new account'));
-    $this->assertText(t('The specified passwords do not match.'), t('Type mismatched passwords display an error message.'));
+    $this->assertText(t('The specified passwords do not match.'), t('Typing mismatched passwords displays an error message.'));
 
     // Enter a correct password.
     $edit['pass[pass1]'] = $new_pass = $this->randomName();
@@ -1314,5 +1314,22 @@ class UserEditTestCase extends DrupalWeb
     variable_set('user_pictures', 1);
     $this->drupalPost("user/$user1->uid/edit", $edit, t('Save'));
     $this->assertRaw(t('The name %name is already taken.', array('%name' => $edit['name'])));
+    
+    // Check that filling out a single password field does not validate.
+    $edit = array();
+    $edit['pass[pass1]'] = '';
+    $edit['pass[pass2]'] = $this->randomName();
+    $this->drupalPost("user/$user1->uid/edit", $edit, t('Save'));
+    $this->assertText(t('The specified passwords do not match.'), t('Typing mismatched passwords displays an error message.'));
+    
+    $edit['pass[pass1]'] = $this->randomName();
+    $edit['pass[pass2]'] = '';
+    $this->drupalPost("user/$user1->uid/edit", $edit, t('Save'));
+    $this->assertText(t('The specified passwords do not match.'), t('Typing mismatched passwords displays an error message.'));
+    
+    $edit['pass[pass1]'] = $new_pass = $this->randomName();
+    $edit['pass[pass2]'] = $new_pass;
+    $this->drupalPost("user/$user1->uid/edit", $edit, t('Save'));
+    $this->assertText(t('The changes have been saved.'), t('Save user password with mismatched type in password confirm.'));
   }
 }