diff --git a/src/jpeg/jconfig.h b/src/jpeg/jconfig.h
index 2d79a744a5..bd5f5db9fa 100644
--- a/src/jpeg/jconfig.h
+++ b/src/jpeg/jconfig.h
@@ -55,8 +55,14 @@
   #undef CHAR_IS_UNSIGNED
 #endif
 
+#ifndef HAVE_STDDEF_H
 #define HAVE_STDDEF_H
+#endif
+
+#ifndef HAVE_STDLIB_H
 #define HAVE_STDLIB_H
+#endif
+
 #undef NEED_BSD_STRINGS
 #undef NEED_SYS_TYPES_H
 #undef NEED_FAR_POINTERS