diff --git a/Makefile b/Makefile
index 57cc399..a211158 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 # Makefile for QEMU.
 
-# Always point to the root of the build tree
-BUILD_DIR=$(PWD)
+# Always point to the root of the build tree (needs GNU make).
+BUILD_DIR=$(CURDIR)
 
 GENERATED_HEADERS = config-host.h trace.h qemu-options.def
 ifeq ($(TRACE_BACKEND),dtrace)