diff --git a/repoconfig.sh b/repoconfig.sh
index 231093a2c66..81c33672d95 100644
--- a/repoconfig.sh
+++ b/repoconfig.sh
@@ -1,6 +1,6 @@
 #! /bin/sh
 # shellcheck disable=SC2034
-NODEJS_VERSION=v16
+NODEJS_VERSION=v20
 GOLANG_VERSION=1.20.3
 GOLANG_DIR=golang/cosmos
 GOLANG_DAEMON=$GOLANG_DIR/build/agd
@@ -15,3 +15,13 @@ golang_version_check() {
   echo 1>&2 "need go version 1.20.2+, 1.21+, or 2+"
   return 1
 }
+
+# Args are major, minor and patch version numbers
+nodejs_version_check() {
+  {
+    [ "$1" -eq 18 ] && [ "$2" -ge 12 ] && return 0
+    [ "$1" -ge 20 ] && [ "$2" -ge 9 ] && return 0
+  } 2> /dev/null
+  echo 1>&2 "need Node.js LTS version ^18.12 or ^20.9, found $1.$2.$3"
+  return 1
+}
diff --git a/scripts/agd-builder.sh b/scripts/agd-builder.sh
index 39a1648dc44..9b09c4bfca2 100755
--- a/scripts/agd-builder.sh
+++ b/scripts/agd-builder.sh
@@ -106,6 +106,12 @@ if $need_nodejs; then
       } 1>&2
       ;;
   esac
+
+  if nodeversion=$(node --version 2> /dev/null); then
+    noderegexp='v([0-9]+)\.([0-9]+)\.([0-9]+)'
+    [[ "$nodeversion" =~ $noderegexp ]] || fatal "illegible node version '$nodeversion'"
+    nodejs_version_check "${BASH_REMATCH[1]}" "${BASH_REMATCH[2]}" "${BASH_REMATCH[3]}" || exit 1
+  fi
 fi
 
 $do_not_build || (
@@ -194,7 +200,9 @@ $do_not_build || (
     test -z "$src" || {
       echo "At least $src is newer than node_modules"
       rm -f "$STAMPS/yarn-built"
-      lazy_yarn install
+      # Ignore engines since we already checked officially supported versions above
+      # UNTIL https://github.com/Agoric/agoric-sdk/issues/9622
+      lazy_yarn install --ignore-engines
     }
 
     stamp=$STAMPS/yarn-built