diff --git a/salt/modules/cmdmod.py b/salt/modules/cmdmod.py
index 233dca8647..794e924216 100644
--- a/salt/modules/cmdmod.py
+++ b/salt/modules/cmdmod.py
@@ -423,6 +423,10 @@ def _run(cmd,
                     env_encoded = env_encoded.encode(__salt_system_encoding__)
                 env_runas = dict(list(zip(*[iter(env_encoded.split(b'\0'))]*2)))
             env_runas.update(env)
+            # Fix platforms like Solaris that don't set a USER env var in the
+            # user's default environment as obtained above.
+            if env_runas.get('USER') != runas:
+                env_runas['USER'] = runas
             env = env_runas
             # Encode unicode kwargs to filesystem encoding to avoid a
             # UnicodeEncodeError when the subprocess is invoked.