diff --git a/Makefile b/Makefile
index 3bd0c08f4b..bbc26e8bd0 100644
--- a/Makefile
+++ b/Makefile
@@ -753,7 +753,7 @@ ifeq ($(uname_S),SunOS)
 	endif
 	INSTALL = /usr/ucb/install
 	TAR = gtar
-	BASIC_CFLAGS += -D__EXTENSIONS__ -D__sun__
+	BASIC_CFLAGS += -D__EXTENSIONS__ -D__sun__ -DHAVE_ALLOCA_H
 endif
 ifeq ($(uname_O),Cygwin)
 	NO_D_TYPE_IN_DIRENT = YesPlease