diff --git a/mps/example/scheme/Makefile.in b/mps/example/scheme/Makefile.in
index fe70cef0158..77ed1f4f0e6 100644
--- a/mps/example/scheme/Makefile.in
+++ b/mps/example/scheme/Makefile.in
@@ -2,7 +2,7 @@
 #
 # $Id$
 
-CFLAGS = @CFLAGS@ @CPPFLAGS@ @LDFLAGS@
+CFLAGS = @CFLAGS@ @CPPFLAGS@ @LDFLAGS@ -std=c99
 
 MPS = ../../code