diff --git a/configure.ac b/configure.ac
index 36958cca..f5cae2e1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1040,7 +1040,8 @@ AC_ARG_WITH([jpeg],
 
 if test x"$with_jpeg" != x"no"; then
   PKG_CHECK_MODULES(JPEG, libjpeg,
-    [with_jpeg="yes (pkg-config)"
+    [AC_DEFINE(HAVE_JPEG,1,[define if you have libjpeg installed.])
+     with_jpeg="yes (pkg-config)"
      PACKAGES_USED="$PACKAGES_USED libjpeg"
     ],
     [FIND_JPEG(