diff --git a/src/supervisor.cpp b/src/supervisor.cpp
index c8a9315..0e627bf 100644
--- a/src/supervisor.cpp
+++ b/src/supervisor.cpp
@@ -539,8 +539,16 @@ bool Supervisor::run_command(Command& cmd) {
         return true;
     }
     case K::Setenv:
-        if (cmd.args.size() >= 1)
-            ::setenv(cmd.args[0].c_str(), cmd.args[1].c_str(), 1);
+        if (cmd.args.size() != 2) {
+            log_status(LogStatus::Failed, "setenv requires NAME and VALUE");
+            return false;
+        }
+        if (::setenv(cmd.args[0].c_str(), cmd.args[1].c_str(), 1) != 0) {
+            log_status(LogStatus::Failed,
+                    "Failed to set environment variable " + cmd.args[0] +
+                    ": " + std::strerror(errno));
+            return false;
+        }
         return true;
     case K::Write: {
         if (cmd.args.size() >= 2) {