diff --git a/llvm/Makefile.config.in b/llvm/Makefile.config.in
index d83e93e72a96..34820fdef243 100644
--- a/llvm/Makefile.config.in
+++ b/llvm/Makefile.config.in
@@ -58,7 +58,8 @@ AR_PATH = @AR@
 #
 # The pathnames of the Flex and Bison programs, respectively.
 #
-BISON    = @YACC@
+YACC     = @YACC@
+BISON    = @BISON@
 FLEX     = @LEX@
 
 #
diff --git a/llvm/autoconf/acinclude.m4 b/llvm/autoconf/acinclude.m4
index 0a64803e2730..972721ce6679 100644
--- a/llvm/autoconf/acinclude.m4
+++ b/llvm/autoconf/acinclude.m4
@@ -6111,6 +6111,10 @@ fi
 # Check for Bison.  This is modified from
 # http://www.gnu.org/software/ac-archive/htmldoc/ac_cxx_namespaces.html
 #
+# This macro verifies that Bison is installed.  If successful, then
+# 1) YACC is set to bison -y (to emulate YACC calls)
+# 2) BISON is set to bison
+#
 AC_DEFUN([AC_PROG_BISON],
 [AC_CACHE_CHECK(,
 ac_cv_has_bison,
@@ -6119,7 +6123,7 @@ ac_cv_has_bison,
 if test "$YACC" != "bison -y"; then
   AC_MSG_ERROR([bison not found but required])
 else
-  AC_SUBST(YACC,[bison],[location of bison])
+  AC_SUBST(BISON,[bison],[location of bison])
 fi
 ])