diff --git a/srcpkgs/gsoap/patches/fix-musl.patch b/srcpkgs/gsoap/patches/fix-musl.patch
index 8a955ac13c..bb9f2c0f4d 100644
--- a/srcpkgs/gsoap/patches/fix-musl.patch
+++ b/srcpkgs/gsoap/patches/fix-musl.patch
@@ -5,6 +5,8 @@ The first patch I think should not be necessary, but is because the same source
 file defines _GNU_SOURCE if gnu-linux and !defined(_GNU_SOURCE) (go read the
 code, it's the first two places _GNU_SOURCE is used in gsoap/stdsoap2.cpp).
 I don't know why, but it seems wrong to me.
+EDIT: Turns out (I was told this) that gcc will define _GNU_SOURCE
+automatically for C++ files. The first patch is definitely necessary.
 
 --- ./gsoap/stdsoap2.cpp.orig
 +++ ./gsoap/stdsoap2.cpp