--- a/libbalsa/html.c
+++ b/libbalsa/html.c
@@ -51,7 +51,9 @@
  * not exist.  Thus, this variable should be set for testing/development,
  * and unset for release builds to avoid leaking the build folder name.
  */
-#define WEB_EXT_CHECK_BUILDDIR	1
+#ifdef WEB_EXT_CHECK_BUILDDIR
+#undef WEB_EXT_CHECK_BUILDDIR
+#endif
 
 
 #define CID_REGEX	"<[^>]*src\\s*=\\s*['\"]?\\s*cid:"
