diff --git a/core/core-packages.el b/core/core-packages.el
index 0e0b1e9bb..153c37b26 100644
--- a/core/core-packages.el
+++ b/core/core-packages.el
@@ -79,6 +79,10 @@ uses a straight or package.el command directly).")
 
 (setq straight-base-dir doom-local-dir
       straight-repository-branch "develop"
+      ;; Since byte-code is rarely compatible across different versions of
+      ;; Emacs, it's best we build them in separate directories, per emacs
+      ;; version.
+      straight-build-dir (format "build-%s" emacs-version)
       straight-cache-autoloads nil ; we already do this, and better.
       ;; Doom doesn't encourage you to modify packages in place. Disabling this
       ;; makes 'doom sync' instant (once everything set up), which is much nicer