diff --git a/clang/lib/Basic/Targets/WebAssembly.h b/clang/lib/Basic/Targets/WebAssembly.h
--- a/clang/lib/Basic/Targets/WebAssembly.h
+++ b/clang/lib/Basic/Targets/WebAssembly.h
@@ -132,7 +132,14 @@
   }
 
   bool hasExtIntType() const override { return true; }
+
+  bool hasProtectedVisibility() const override {
+    // For compatibility, continue to advertise "protected" support for
+    // Emscripten targets.
+    return getTriple().isOSEmscripten();
+  }
 };
+
 class LLVM_LIBRARY_VISIBILITY WebAssembly32TargetInfo
     : public WebAssemblyTargetInfo {
 public:
diff --git a/llvm/docs/ReleaseNotes.rst b/llvm/docs/ReleaseNotes.rst
--- a/llvm/docs/ReleaseNotes.rst
+++ b/llvm/docs/ReleaseNotes.rst
@@ -144,8 +144,14 @@
 Changes to the WebAssembly Target
 ---------------------------------
 
-During this release ...
-
+* Programs which don't have a "main" function, called "reactors" are now
+  properly supported, with a new `-mexec-model=reactor` flag. Programs which
+  previously used `-Wl,--no-entry` to avoid having a main function should
+  switch to this new flag, so that static initialization is properly
+  performed.
+
+* `__attribute__((visibility("protected")))` now evokes a warning, as
+  WebAssembly does not support "protected" visibility.
 
 Changes to the OCaml bindings
 -----------------------------