diff --git a/package/pkg-generic.mk b/package/pkg-generic.mk
index dab455c400..0c9c7ab744 100644
--- a/package/pkg-generic.mk
+++ b/package/pkg-generic.mk
@@ -938,6 +938,12 @@ endif
 	$(1)-source \
 	$(1)-source-check
 
+ifneq ($$($(2)_SOURCE),)
+ifeq ($$($(2)_SITE),)
+$$(error $(2)_SITE cannot be empty when $(2)_SOURCE is not)
+endif
+endif
+
 ifeq ($$(patsubst %/,ERROR,$$($(2)_SITE)),ERROR)
 $$(error $(2)_SITE ($$($(2)_SITE)) cannot have a trailing slash)
 endif