diff --git a/Makefile b/Makefile
index d9786d2ac05..837c2d72228 100644
--- a/Makefile
+++ b/Makefile
@@ -113,7 +113,8 @@ all::
 ifeq ($(BuildMode),Debug)
 	$(Echo) '*****' Note: Debug build can be 10 times slower than an
 	$(Echo) '*****' optimized build. Use 'make ENABLE_OPTIMIZED=1' to
-	$(Echo) '*****' make an optimized build.
+	$(Echo) '*****' make an optimized build. Alternatively you can
+	$(Echo) '*****' configure with --enable-optimized.
 endif
 
 check-llvm2cpp:
@@ -143,3 +144,7 @@ build-for-llvm-top:
 
 .PHONY: srpm rpm
 
+# declare all targets at this level to be serial:
+
+.NOTPARALLEL:
+