diff --git a/var/spack/repos/builtin/packages/simgrid/package.py b/var/spack/repos/builtin/packages/simgrid/package.py
index 122d1d9de0e..21f910bb8ca 100644
--- a/var/spack/repos/builtin/packages/simgrid/package.py
+++ b/var/spack/repos/builtin/packages/simgrid/package.py
@@ -20,6 +20,7 @@ class Simgrid(CMakePackage):
 
     license("LGPL-2.1-or-later")
 
+    version("4.0", sha256="c9f07122d43f61f1f0a21be2e42ef2cd6290abbf9b697926430f44ca2786bdea")
     version("3.36", sha256="cfdf6b98270c59be5c112457793c540bdd6a10deece91cbdb4793fbda190b95d")
     version("3.35", sha256="b4570d3de18d319cbd2e16c5a669f90760307673c0cc9940d4d11cfc537e69a8")
     version("3.34", sha256="161f1c6c0ebb588c587aea6388114307bb31b3c6d5332fa3dc678151f1d0564d")
@@ -140,6 +141,8 @@ class Simgrid(CMakePackage):
         " please use an older release (e.g., %gcc@:9).",
     )
 
+    conflicts("+msg", when="@3.34:", msg="MSG was removed from SimGrid v3.33.")
+
     def setup_dependent_package(self, module, dep_spec):
         if self.spec.satisfies("+smpi"):
             self.spec.smpicc = join_path(self.prefix.bin, "smpicc")