diff --git a/meta/classes-global/base.bbclass b/meta/classes-global/base.bbclass
index 4ac7bafefa..b6940bbb6f 100644
--- a/meta/classes-global/base.bbclass
+++ b/meta/classes-global/base.bbclass
@@ -428,11 +428,6 @@ python () {
     oe.utils.features_backfill("DISTRO_FEATURES", d)
     oe.utils.features_backfill("MACHINE_FEATURES", d)
 
-    if d.getVar("S")[-1] == '/':
-        bb.warn("Recipe %s sets S variable with trailing slash '%s', remove it" % (d.getVar("PN"), d.getVar("S")))
-    if d.getVar("B")[-1] == '/':
-        bb.warn("Recipe %s sets B variable with trailing slash '%s', remove it" % (d.getVar("PN"), d.getVar("B")))
-
     # To add a recipe to the skip list , set:
     #   SKIP_RECIPE[pn] = "message"
     pn = d.getVar('PN')
diff --git a/meta/classes-global/insane.bbclass b/meta/classes-global/insane.bbclass
index 42ed1a24a7..99736830b9 100644
--- a/meta/classes-global/insane.bbclass
+++ b/meta/classes-global/insane.bbclass
@@ -1609,6 +1609,10 @@ python () {
         bb.fatal("Using S = ${WORKDIR} is no longer supported")
     if builddir == workdir:
         bb.fatal("Using B = ${WORKDIR} is no longer supported")
+    if sourcedir[-1] == '/':
+        bb.warn("Recipe %s sets S variable with trailing slash '%s', remove it" % (d.getVar("PN"), d.getVar("S")))
+    if builddir[-1] == '/':
+        bb.warn("Recipe %s sets B variable with trailing slash '%s', remove it" % (d.getVar("PN"), d.getVar("B")))
 
     # Some people mistakenly use DEPENDS:${PN} instead of DEPENDS and wonder
     # why it doesn't work.