diff --git a/omicron/ssg/config.py b/omicron/ssg/config.py
index 92432c2..7b104e0 100644
--- a/omicron/ssg/config.py
+++ b/omicron/ssg/config.py
@@ -42,6 +42,9 @@ class SiteConfig:
         else:
             path = Path("/")
 
+        if not path.is_absolute():
+            raise ConfigError("base_url config property must not be a relative path")
+
         return (origin, path)
 
     @staticmethod
diff --git a/omicron/ssg/site.py b/omicron/ssg/site.py
index f944d2d..fc00657 100644
--- a/omicron/ssg/site.py
+++ b/omicron/ssg/site.py
@@ -183,8 +183,6 @@ class Site:
                 "base_url config value is missing a domain name, "
                 "can't add canonical url to content"
             )
-        if not self.config.base_dir.is_absolute():
-            raise ConfigError("base_url config value must be an absolute path")
         self.discover()
         outputs: list[Output] = [*self.directories, *self.content]
         for output in sorted(outputs, key=lambda o: o.destination.as_posix()):