diff --git a/src/doc/Doxyfile b/src/doc/Doxyfile
index 8ea35bd4be..55787ed0c0 100644
--- a/src/doc/Doxyfile
+++ b/src/doc/Doxyfile
@@ -2204,6 +2204,7 @@ PREDEFINED             = DOXYGEN_SHOULD_SKIP_THIS \
                          OIIO_NODISCARD:= \
                          OIIO_NODISCARD_ERROR:= \
                          OIIO_DEPRECATED(x)=[[deprecated]] \
+                         OIIO_DEPRECATED_EXTERNAL(x)=[[deprecated]] \
                          OIIO_FORMAT_DEPRECATED:= \
                          OIIO_FORCEINLINE=inline \
                          IMATH_HALF_H_=1 \