diff --git a/lib/spack/docs/conf.py b/lib/spack/docs/conf.py
index 55848106dec..cbac5a4f4d4 100644
--- a/lib/spack/docs/conf.py
+++ b/lib/spack/docs/conf.py
@@ -74,6 +74,7 @@
     "--force",  # Overwrite existing files
     "--no-toc",  # Don't create a table of contents file
     "--output-dir=.",  # Directory to place all output
+    "--module-first",  # emit module docs before submodule docs
 ]
 sphinx_apidoc(apidoc_args + ["_spack_root/lib/spack/spack"])
 sphinx_apidoc(apidoc_args + ["_spack_root/lib/spack/llnl"])