diff --git a/configure.ac b/configure.ac
index a627feb..57c9a5d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -60,6 +60,7 @@ AS_IF([test x"$FOUND_GUIX" = x""],
 # settings by sourcing it.
 printf '#!/usr/bin/env bash\n' > config.sh
 printf '# This file is generated by configure.ac\n' >> config.sh
+printf 'GUIX_BUILD_MAX_CORES=%s\n' "$GUIX_BUILD_MAX_CORES" >> config.sh
 printf 'GUIX_REVISION=%s\n' "$GUIX_REVISION" >> config.sh
 chmod +x config.sh