Index: support/devel/sak/validate/syntax.tcl
==================================================================
--- support/devel/sak/validate/syntax.tcl
+++ support/devel/sak/validate/syntax.tcl
@@ -192,11 +192,13 @@
 	if {[string equal $c rename]}    continue
 	if {[string equal $c namespace]} continue
 	interp eval $ip [list ::rename $c {}]
     }
 
-    interp eval $ip [list ::namespace delete ::tcl]
+    if {![package vsatisfies [package present Tcl] 8.6]} {
+	interp eval $ip [list ::namespace delete ::tcl]
+    }
     interp eval $ip [list ::rename namespace {}]
     interp eval $ip [list ::rename rename    {}]
 
     foreach m {
 	pcx::register unknown

Index: support/devel/sak/validate/testsuites.tcl
==================================================================
--- support/devel/sak/validate/testsuites.tcl
+++ support/devel/sak/validate/testsuites.tcl
@@ -137,11 +137,13 @@
 	if {[string equal $c rename]}    continue
 	if {[string equal $c namespace]} continue
 	interp eval $ip [list ::rename $c {}]
     }
 
-    interp eval $ip [list ::namespace delete ::tcl]
+    if {![package vsatisfies [package present Tcl] 8.6]} {
+	interp eval $ip [list ::namespace delete ::tcl]
+    }
     interp eval $ip [list ::rename namespace {}]
     interp eval $ip [list ::rename rename    {}]
 
     foreach m {
 	testing unknown useLocal useLocalKeep useAccel