diff --git a/Makefile.include b/Makefile.include
index 9b18c6a0fe..f1770191f3 100644
--- a/Makefile.include
+++ b/Makefile.include
@@ -1,10 +1,9 @@
 MATCH_MAKE_VERSION = 4.%
 
 ifeq (,$(filter $(MATCH_MAKE_VERSION),$(MAKE_VERSION)))
-  $(warning GNU Make $(MAKE_VERSION) is DEPRECATED in RIOT. Support for \
-	    versions less than $(MATCH_MAKE_VERSION) will be removed in \
-	    release 2020.01. Please upgrade your system to use GNU Make \
-	    $(MATCH_MAKE_VERSION) or later.)
+  $(error GNU Make $(MAKE_VERSION) is not supported by RIOT since release \
+      2020.01. Please upgrade your system to use GNU Make \
+      $(MATCH_MAKE_VERSION) or later.)
 endif
 
 # 'Makefile.include' directory, must be evaluated before other 'include'