diff --git a/build/proof-params/mkparamfetch.sh b/build/proof-params/mkparamfetch.sh
index b503e22ef..a9f8023ea 100755
--- a/build/proof-params/mkparamfetch.sh
+++ b/build/proof-params/mkparamfetch.sh
@@ -2,5 +2,19 @@
 
 set -euo pipefail
 
-sed "s/{{PARAMSJSON}}/$(base64 build/proof-params/parameters.json -w 0)/g" build/proof-params/paramfetch.sh.template > ./build/paramfetch.sh
+function b64() {
+	f="$1"
+	case `uname` in
+	Darwin)
+		base64 -i "$f"
+	;;
+	Linux)
+		base64 "$f" -w 0
+	;;
+	esac
+	printf "unsupported system" 1>&2
+	exit 1
+}
+
+sed "s/{{PARAMSJSON}}/$(b64 build/proof-params/parameters.json)/g" build/proof-params/paramfetch.sh.template > ./build/paramfetch.sh
 chmod +x ./build/paramfetch.sh
diff --git a/chain/sync.go b/chain/sync.go
index d3028f057..0c224b84a 100644
--- a/chain/sync.go
+++ b/chain/sync.go
@@ -546,7 +546,7 @@ loop:
 			blockSet = append(blockSet, b)
 		}
 
-		syncer.syncState.SetHeight(blks[len(blockSet)-1].Height())
+		syncer.syncState.SetHeight(blks[len(blks)-1].Height())
 		at = blks[len(blks)-1].Parents()
 	}