diff --git a/core/definitions.mk b/core/definitions.mk
index a93979a..140db60 100644
--- a/core/definitions.mk
+++ b/core/definitions.mk
@@ -2678,9 +2678,9 @@
 ###########################################################
 
 # $(1): The file to check
-ifndef get-file-size
-$(error HOST_OS must define get-file-size)
-endif
+define get-file-size
+stat -c "%s" "$(1)" | tr -d '\n'
+endef
 
 # $(1): The file(s) to check (often $@)
 # $(2): The partition size.