diff --git a/mkdocs/config/config_options.py b/mkdocs/config/config_options.py
index 8caf16ad5e..7074947967 100644
--- a/mkdocs/config/config_options.py
+++ b/mkdocs/config/config_options.py
@@ -59,7 +59,12 @@ def validate(self, value):
         return self.run_validation(value)
 
     def run_validation(self, value):
-        Config.validate(self)
+        failed, self.warnings = Config.validate(self)
+        if len(failed) > 0:
+            # get the first failing one
+            key, err = failed[0]
+            raise ValidationError(f"Sub-option {key!r} configuration error: {err}")
+
         return self