diff --git a/swh/loader/cli.py b/swh/loader/cli.py
--- a/swh/loader/cli.py
+++ b/swh/loader/cli.py
@@ -77,7 +77,7 @@
 
     ctx.obj["config"] = read(config_file)
     logger.debug("config_file: %s", config_file)
-    logger.debug("config: ", ctx.obj["config"])
+    logger.debug("config: %s", ctx.obj["config"])
 
 
 @loader.command(name="run", context_settings=CONTEXT_SETTINGS)
@@ -93,7 +93,10 @@
 
     conf = ctx.obj.get("config", {})
     if "storage" not in conf:
-        raise ValueError("Missing storage configuration key")
+        logger.info(
+            "No storage configuration detected, using an in-memory storage instead."
+        )
+        conf["storage"] = {"cls": "memory"}
 
     (_, kw) = parse_options(options)
     logger.debug(f"kw: {kw}")