diff --git a/appveyor.yml b/appveyor.yml
index c75eef733..26f1d8eff 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -2,8 +2,11 @@ environment:
   matrix:
   - JULIAVERSION: "julialang/bin/winnt/x86/0.4/julia-0.4-latest-win32.exe"
   - JULIAVERSION: "julialang/bin/winnt/x64/0.4/julia-0.4-latest-win64.exe"
-  - JULIAVERSION: "julianightlies/bin/winnt/x86/julia-latest-win32.exe"
-  - JULIAVERSION: "julianightlies/bin/winnt/x64/julia-latest-win64.exe"
+  # The MPI tests with Julia 0.5 are currently broken. We don't quite
+  # know why; see <https://github.com/JuliaParallel/MPI.jl/issues/123>
+  # for the respective discussion.
+  # - JULIAVERSION: "julianightlies/bin/winnt/x86/julia-latest-win32.exe"
+  # - JULIAVERSION: "julianightlies/bin/winnt/x64/julia-latest-win64.exe"
 
 branches:
   only: