diff --git a/Makefile.include b/Makefile.include
index da39ecaadf..b93ab1d273 100644
--- a/Makefile.include
+++ b/Makefile.include
@@ -106,6 +106,9 @@ OS := $(shell uname)
 # set python path, e.g. for tests
 PYTHONPATH := $(RIOTBASE)/dist/pythonlibs/:$(PYTHONPATH)
 
+# Basic utilities included before anything else
+include $(RIOTMAKE)/utils/checks.mk
+
 # Include Docker settings near the top because we need to build the environment
 # command line before some of the variable origins are overwritten below when
 # using abspath, strip etc.
diff --git a/makefiles/tools/serial.inc.mk b/makefiles/tools/serial.inc.mk
index 215a5057e8..84144166e0 100644
--- a/makefiles/tools/serial.inc.mk
+++ b/makefiles/tools/serial.inc.mk
@@ -1,12 +1,9 @@
 # set default port depending on operating system
 OS := $(shell uname)
 ifeq ($(OS),Linux)
-  PORT ?= $(PORT_LINUX)
+  PORT ?= $(call ensure_value,$(PORT_LINUX),No port set)
 else ifeq ($(OS),Darwin)
-  PORT ?= $(PORT_DARWIN)
-endif
-ifeq ($(PORT),)
-  $(info Warning: no PORT set!)
+  PORT ?= $(call ensure_value,$(PORT_DARWIN),No port set)
 endif
 
 export BAUD ?= 115200