diff -urp blt2.5/generic/tkButton.c blt2.5-tk8.6/generic/tkButton.c
--- blt2.5/generic/tkButton.c	2010-11-17 17:16:52.000000000 +0100
+++ blt2.5-tk8.6/generic/tkButton.c	2016-03-15 16:41:27.283293880 +0100
@@ -844,8 +844,6 @@
 
 static Pixmap DrawAALines(Button *butPtr, Drawable pixmap, XColor *color, XPoint *polyPoints, int numPoints);
 
-EXTERN int TkCopyAndGlobalEval _ANSI_ARGS_((Tcl_Interp *interp, char *script));
-
 #if (TK_MAJOR_VERSION > 4)
 EXTERN void TkComputeAnchor _ANSI_ARGS_((Tk_Anchor anchor, Tk_Window tkwin, 
 	int padX, int padY, int innerWidth, int innerHeight, int *xPtr, 
@@ -3097,7 +3095,7 @@
 	}
     }
     if ((butPtr->type != TYPE_LABEL) && (butPtr->command != NULL)) {
-	return TkCopyAndGlobalEval(butPtr->interp, butPtr->command);
+	return Tcl_EvalObjEx(butPtr->interp, butPtr->command, TCL_EVAL_GLOBAL);
     }
     return TCL_OK;
 }