diff --git a/src/apps.js b/src/apps.js
index 58dde5afa..624602340 100644
--- a/src/apps.js
+++ b/src/apps.js
@@ -244,7 +244,7 @@ function validatePortBindings(portBindings, manifest) {
     const udpPorts = manifest.udpPorts || { };
 
     for (const portName in portBindings) {
-        if (!/^[a-zA-Z0-9_]+$/.test(portName)) return new BoxError(BoxError.BAD_FIELD, `${portName} is not a valid environment variable in portBindings`);
+        if (!/^[A-Z0-9_]+$/.test(portName)) return new BoxError(BoxError.BAD_FIELD, `${portName} is not a valid environment variable in portBindings`);
 
         const hostPort = portBindings[portName];
         if (!Number.isInteger(hostPort)) return new BoxError(BoxError.BAD_FIELD, `${hostPort} is not an integer in ${portName} portBindings`);