diff --git a/ui/desktop/src/components/settings_v2/extensions/modal/EnvVarsSection.tsx b/ui/desktop/src/components/settings_v2/extensions/modal/EnvVarsSection.tsx
index 45380405..0dd56773 100644
--- a/ui/desktop/src/components/settings_v2/extensions/modal/EnvVarsSection.tsx
+++ b/ui/desktop/src/components/settings_v2/extensions/modal/EnvVarsSection.tsx
@@ -30,6 +30,7 @@ export default function EnvVarsSection({
   const handleAdd = () => {
     const keyEmpty = !newKey.trim();
     const valueEmpty = !newValue.trim();
+    const keyHasSpaces = newKey.includes(' ');
 
     if (keyEmpty || valueEmpty) {
       setInvalidFields({
@@ -40,6 +41,15 @@ export default function EnvVarsSection({
       return;
     }
 
+    if (keyHasSpaces) {
+      setInvalidFields({
+        key: true,
+        value: false,
+      });
+      setValidationError('Variable name cannot contain spaces');
+      return;
+    }
+
     setValidationError(null);
     setInvalidFields({ key: false, value: false });
     onAdd(newKey, newValue);