diff --git a/meta/classes-global/sanity.bbclass b/meta/classes-global/sanity.bbclass
index 1a490f8d61..3142ff61f2 100644
--- a/meta/classes-global/sanity.bbclass
+++ b/meta/classes-global/sanity.bbclass
@@ -984,6 +984,10 @@ def check_sanity_everybuild(status, d):
             "Please set TMPDIR to a clean path with no trailing slash or "
             "consecutive slashes (e.g. %s).\n" % (tmpdir, os.path.normpath(tmpdir)))
 
+    # Check whether the SOURCE_MIRROR_URL variable, belonging to the 'own-mirrors' class, is defined
+    if oe.utils.inherits(d, 'own-mirrors') and not d.getVar('SOURCE_MIRROR_URL'):
+        status.addresult("own-mirrors is enabled, but SOURCE_MIRROR_URL is not defined")
+
     # Check the format of MIRRORS, PREMIRRORS and SSTATE_MIRRORS
     import re
     mirror_vars = ['MIRRORS', 'PREMIRRORS', 'SSTATE_MIRRORS']