diff --git a/lib/src/sdk_env.dart b/lib/src/sdk_env.dart
index 7d6187dc2..583f32b29 100644
--- a/lib/src/sdk_env.dart
+++ b/lib/src/sdk_env.dart
@@ -471,7 +471,7 @@ class ToolEnvironment {
             'global',
             'activate',
             'dartdoc',
-            if (_dartdocVersion != null) _dartdocVersion!,
+            if (_dartdocVersion != null) _dartdocVersion,
           ],
           environment: {
             ..._dartSdk.environment,