diff --git a/qutebrowser/config/configtypes.py b/qutebrowser/config/configtypes.py
index 23909b9c1..d3f0b0d8d 100644
--- a/qutebrowser/config/configtypes.py
+++ b/qutebrowser/config/configtypes.py
@@ -1110,8 +1110,15 @@ class SearchEngineUrl(BaseType):
                 return
             else:
                 raise configexc.ValidationError(value, "may not be empty!")
+
         if '{}' not in value:
             raise configexc.ValidationError(value, "must contain \"{}\"")
+        try:
+            value.format("")
+        except KeyError:
+            raise configexc.ValidationError(
+                value, "may not contain {...} (use {{ and }} for literal {/})")
+
         url = QUrl(value.replace('{}', 'foobar'))
         if not url.isValid():
             raise configexc.ValidationError(value, "invalid url, {}".format(
diff --git a/tests/config/test_configtypes.py b/tests/config/test_configtypes.py
index 6b6a08594..edb0bb8cb 100644
--- a/tests/config/test_configtypes.py
+++ b/tests/config/test_configtypes.py
@@ -1881,6 +1881,11 @@ class TestSearchEngineUrl:
         with pytest.raises(configexc.ValidationError):
             self.t.validate(':{}')
 
+    def test_validate_format_string(self):
+        """Test validate with a {foo} format string."""
+        with pytest.raises(configexc.ValidationError):
+            self.t.validate('foo{bar}baz{}')
+
     def test_transform_empty(self):
         """Test transform with an empty value."""
         assert self.t.transform('') is None