diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 9d772d1b4..72c144abd 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -14,7 +14,12 @@ jobs:
 
     strategy:
       matrix:
-        go: [oldstable, stable]
+        # our oldest (officially) supported version and the two upstream-supported versions
+        go: [1.21.x, oldstable, stable]
+
+    env:
+      # avoid downloading any alternate toolchains (https://go.dev/doc/toolchain)
+      GOTOOLCHAIN: local
 
     steps:
       - name: checkout source code