diff --git a/ext/standard/config.m4 b/ext/standard/config.m4
index d9e0bb7cc2c..d328979c595 100644
--- a/ext/standard/config.m4
+++ b/ext/standard/config.m4
@@ -170,7 +170,7 @@ main() {
   ac_cv_crypt_blowfish=no
 ])])
 
-AC_CACHE_CHECK(for SHA512 crypt, ac_cv_crypt_SHA512,[
+AC_CACHE_CHECK(for SHA512 crypt, ac_cv_crypt_sha512,[
 AC_TRY_RUN([
 #if HAVE_UNISTD_H
 #include <unistd.h>
@@ -192,14 +192,14 @@ main() {
 	exit(0);
 #endif
 }],[
-  ac_cv_crypt_SHA512=yes
+  ac_cv_crypt_sha512=yes
 ],[
-  ac_cv_crypt_SHA512=no
+  ac_cv_crypt_sha512=no
 ],[
-  ac_cv_crypt_SHA512=no
+  ac_cv_crypt_sha512=no
 ])])
 
-AC_CACHE_CHECK(for SHA256 crypt, ac_cv_crypt_SHA256,[
+AC_CACHE_CHECK(for SHA256 crypt, ac_cv_crypt_sha256,[
 AC_TRY_RUN([
 #if HAVE_UNISTD_H
 #include <unistd.h>
@@ -222,11 +222,11 @@ main() {
 	exit(0);
 #endif
 }],[
-  ac_cv_crypt_SHA256=yes
+  ac_cv_crypt_sha256=yes
 ],[
-  ac_cv_crypt_SHA256=no
+  ac_cv_crypt_sha256=no
 ],[
-  ac_cv_crypt_SHA256=no
+  ac_cv_crypt_sha256=no
 ])])