diff --git a/configure.ac b/configure.ac
--- a/configure.ac
+++ b/configure.ac
@@ -112,6 +112,13 @@ AC_SUBST([JPEG_LIBS])
 AC_DEFINE_UNQUOTED([HAVE_JPEGLIB], $HAVE_JPEGLIB, [Define to 1 if you have libjpeg installed])
 
 PKG_CHECK_MODULES(SSL, "openssl", [HAVE_OPENSSL=1])
+AC_DEFUN([PKG_CHECK_VAR],
+  [AC_REQUIRE([PKG_PROG_PKG_CONFIG])
+   AC_ARG_VAR([$1], [value of $3 for $2, overriding pkg-config])
+   _PKG_CONFIG([$1], [variable="][$3]["], [$2])
+   AS_VAR_COPY([$1], [pkg_cv_][$1])
+   AS_VAR_IF([$1], [""], [$5], [$4])
+  ])# PKG_CHECK_VAR
 PKG_CHECK_VAR(SSL_PREFIX, "openssl", "exec_prefix",, AC_MSG_ERROR([Could not find exec_prefix for openssl]))
 AC_DEFINE_UNQUOTED([HAVE_OPENSSL], $HAVE_OPENSSL, [Define to 1 if you have OpenSSL installed])
 AC_SUBST(SSL_PREFIX)