diff --git a/var/spack/repos/builtin/packages/phist/package.py b/var/spack/repos/builtin/packages/phist/package.py
index 0c67b0165d4a3ef940ce54baa35d6ad68bb746fb..49055440c94146a08990a25c34b9ae2d7c4a47b7 100644
--- a/var/spack/repos/builtin/packages/phist/package.py
+++ b/var/spack/repos/builtin/packages/phist/package.py
@@ -111,6 +111,10 @@ class Phist(CMakePackage):
     # required a separate package
     conflicts('+fortran', when='@:1.6.99')
 
+    # older gcc's may produce incorrect SIMD code and fail
+    # to compile some OpenMP statements
+    conflicts('%gcc@:4.9.1')
+
     def cmake_args(self):
         spec = self.spec