diff --git a/support/testing/infra/builder.py b/support/testing/infra/builder.py
index a475bb0a30..905b127c91 100644
--- a/support/testing/infra/builder.py
+++ b/support/testing/infra/builder.py
@@ -17,6 +17,10 @@ class Builder(object):
         config_file = os.path.join(self.builddir, ".config")
         with open(config_file, "w+") as cf:
             cf.write(self.config)
+        # dump the defconfig to the logfile for easy debugging
+        self.logfile.write("> start defconfig\n" + self.config +
+                           "> end defconfig\n")
+        self.logfile.flush()
 
         cmd = ["make",
                "O={}".format(self.builddir),