diff --git a/contrib/hgk b/contrib/hgk
--- a/contrib/hgk
+++ b/contrib/hgk
@@ -109,7 +109,12 @@ bind all <MouseWheel> [list ::tk::MouseW
 # end of win32 section
 } else {
 
-if {[ttk::style theme use] eq "default"} {
+if {[catch {
+    set theme [ttk::style theme use]
+}]} {
+    set theme $::ttk::currentTheme
+}
+if {$theme eq "default"} {
     ttk::style theme use clam
 }