diff --git a/generic/tkWindow.c b/generic/tkWindow.c
index fa25553..ad45598 100644
--- a/generic/tkWindow.c
+++ b/generic/tkWindow.c
@@ -1045,6 +1045,7 @@ TkCreateMainWindow(
 
     Tcl_SetVar2(interp, "tk_patchLevel", NULL, TK_PATCH_LEVEL, TCL_GLOBAL_ONLY);
     Tcl_SetVar2(interp, "tk_version",    NULL, TK_VERSION,     TCL_GLOBAL_ONLY);
+    Tcl_SetVar2(interp, "tk_library",    NULL, TK_LIBRARY,     TCL_GLOBAL_ONLY);
 
     tsdPtr->numMainWindows++;
     return tkwin;
diff --git a/unix/Makefile.in b/unix/Makefile.in
index e98070e..f417753 100644
--- a/unix/Makefile.in
+++ b/unix/Makefile.in
@@ -1033,7 +1033,7 @@ tkVisual.o: $(GENERIC_DIR)/tkVisual.c
 	$(CC) -c $(CC_SWITCHES) $(GENERIC_DIR)/tkVisual.c
 
 tkWindow.o: $(GENERIC_DIR)/tkWindow.c tkUuid.h
-	$(CC) -c $(CC_SWITCHES) -I. $(GENERIC_DIR)/tkWindow.c
+	$(CC) -c $(CC_SWITCHES) -I. -DTK_LIBRARY=\"${TK_LIBRARY}\" $(GENERIC_DIR)/tkWindow.c
 
 tkButton.o: $(GENERIC_DIR)/tkButton.c
 	$(CC) -c $(CC_SWITCHES) $(GENERIC_DIR)/tkButton.c