diff --git a/GNUmakefile b/GNUmakefile
index 2f09d5948..bee87496a 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -7,7 +7,8 @@ EXTERNAL_TOOLS=\
 	golang.org/x/tools/cmd/cover \
 	golang.org/x/tools/cmd/vet \
 	github.com/axw/gocov/gocov \
-	gopkg.in/matm/v1/gocov-html
+	gopkg.in/matm/v1/gocov-html \
+	github.com/ugorji/go/codec/codecgen
 
 GOFILES_NOVENDOR = $(shell find . -type f -name '*.go' -not -path "./vendor/*")