diff --git a/Makefile b/Makefile
index e8c86a0..a3be0af 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,8 @@ GOSRC_APP        := metric-collector.go
 GOSRC_COLLECTORS := $(wildcard collectors/*.go)
 GOSRC_SINKS      := $(wildcard sinks/*.go)
 GOSRC_RECEIVERS  := $(wildcard receivers/*.go)
-GOSRC            := $(GOSRC_APP) $(GOSRC_COLLECTORS) $(GOSRC_SINKS) $(GOSRC_RECEIVERS)
+GOSRC_INTERNAL   := $(wildcard internal/*/*.go)
+GOSRC            := $(GOSRC_APP) $(GOSRC_COLLECTORS) $(GOSRC_SINKS) $(GOSRC_RECEIVERS) $(GOSRC_INTERNAL)
 
 .PHONY: all
 all: $(APP)
@@ -23,6 +24,7 @@ fmt:
 	go fmt $(GOSRC_COLLECTORS)
 	go fmt $(GOSRC_SINKS)
 	go fmt $(GOSRC_RECEIVERS)
+	go fmt $(GOSRC_INTERNAL)
 	go fmt $(GOSRC_APP)
 	find . -name "*.go" -exec go fmt {} \;