diff --git a/src/cfgparse.y b/src/cfgparse.y
index 868640e0..7efecc92 100644
--- a/src/cfgparse.y
+++ b/src/cfgparse.y
@@ -1071,11 +1071,23 @@ assign:
         char *separator = NULL;
         if ((separator = strchr(criteria, '/')) != NULL) {
             *(separator++) = '\0';
-            match->title = regex_new(separator);
+            char *pattern;
+            if (asprintf(&pattern, "(?i)%s", separator) == -1) {
+                ELOG("asprintf failed\n");
+                break;
+            }
+            match->title = regex_new(pattern);
+            free(pattern);
             printf("  title = %s\n", separator);
         }
         if (*criteria != '\0') {
-            match->class = regex_new(criteria);
+            char *pattern;
+            if (asprintf(&pattern, "(?i)%s", criteria) == -1) {
+                ELOG("asprintf failed\n");
+                break;
+            }
+            match->class = regex_new(pattern);
+            free(pattern);
             printf("  class = %s\n", criteria);
         }
         free(criteria);
diff --git a/testcases/t/66-assign.t b/testcases/t/66-assign.t
index 776710e7..25855b58 100644
--- a/testcases/t/66-assign.t
+++ b/testcases/t/66-assign.t
@@ -182,6 +182,46 @@ exit_gracefully($process->pid);
 
 sleep 0.25;
 
+#####################################################################
+# make sure that assignments are case-insensitive in the old syntax.
+#####################################################################
+
+$config = <<EOT;
+# i3 config file (v4)
+font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
+assign "special" → ~
+EOT
+
+$process = launch_with_config($config);
+
+$tmp = fresh_workspace;
+
+ok(@{get_ws_content($tmp)} == 0, 'no containers yet');
+my $workspaces = get_workspace_names;
+ok(!("targetws" ~~ @{$workspaces}), 'targetws does not exist yet');
+
+my $window = $x->root->create_child(
+    class => WINDOW_CLASS_INPUT_OUTPUT,
+    rect => [ 0, 0, 30, 30 ],
+    background_color => '#0000ff',
+);
+
+$window->_create;
+set_wm_class($window->id, 'SPEcial', 'SPEcial');
+$window->name('special window');
+$window->map;
+sleep 0.25;
+
+my $content = get_ws($tmp);
+ok(@{$content->{nodes}} == 0, 'no tiling cons');
+ok(@{$content->{floating_nodes}} == 1, 'one floating con');
+
+$window->destroy;
+
+exit_gracefully($process->pid);
+
+sleep 0.25;
+
 #####################################################################
 # regression test: dock clients with floating assignments should not crash
 # (instead, nothing should happen - dock clients can’t float)