diff --git a/.github/workflows/DowngradeSublibraries.yml b/.github/workflows/DowngradeSublibraries.yml
index 33f9c61cc..c41e04373 100644
--- a/.github/workflows/DowngradeSublibraries.yml
+++ b/.github/workflows/DowngradeSublibraries.yml
@@ -18,7 +18,10 @@ jobs:
     uses: "SciML/.github/.github/workflows/sublibrary-downgrade.yml@v1"
     secrets: "inherit"
     with:
-      julia-version: "lts"
+      # The sublibrary downgrade resolver passes julia-version straight to
+      # `resolve.jl --julia=`, which requires a numeric registry-compat spec and
+      # rejects the "lts" channel alias. Pin to the numeric sublibrary floor.
+      julia-version: "1.10"
       # SymbolicAnalysis skipped: 0.3.x doesn't support Symbolics 7 (required by
       # ModelingToolkit 11). Stdlibs and in-repo sublibraries are auto-populated by
       # the centralized workflow.