diff --git a/pkg/compiler/test/analyses/api_allowed.json b/pkg/compiler/test/analyses/api_allowed.json
index 645ff86..96aac80 100644
--- a/pkg/compiler/test/analyses/api_allowed.json
+++ b/pkg/compiler/test/analyses/api_allowed.json
@@ -69,12 +69,6 @@
   "org-dartlang-sdk:///lib/io/link.dart": {
     "Dynamic invocation of '[]'.": 3
   },
-  "org-dartlang-sdk:///lib/io/platform_impl.dart": {
-    "Dynamic invocation of 'indexOf'.": 1,
-    "Dynamic invocation of '>'.": 1,
-    "Dynamic invocation of 'substring'.": 2,
-    "Dynamic invocation of '+'.": 1
-  },
   "org-dartlang-sdk:///lib/io/secure_server_socket.dart": {
     "Dynamic update to 'dart.io::_owner'.": 1
   },
diff --git a/sdk/lib/io/platform_impl.dart b/sdk/lib/io/platform_impl.dart
index 48d89ef..0fca80f 100644
--- a/sdk/lib/io/platform_impl.dart
+++ b/sdk/lib/io/platform_impl.dart
@@ -81,24 +81,29 @@
   static Map<String, String> get environment {
     if (_environmentCache == null) {
       var env = _environment();
-      if (env is! OSError) {
+      if (env is Iterable<Object?>) {
         var isWindows = operatingSystem == 'windows';
         var result = isWindows
             ? new _CaseInsensitiveStringMap<String>()
             : new Map<String, String>();
-        for (var str in env) {
-          if (str == null) {
+        for (var environmentEntry in env) {
+          if (environmentEntry == null) {
             continue;
           }
+          // TODO(kallentu): [_environment()] emits Iterable<dynamic> which is
+          // why the cast and check is needed. Every element is a String,
+          // however, so refactor [_environment()] at some point to emit
+          // Iterable<String>s instead.
+          var text = environmentEntry as String;
           // The Strings returned by [_environment()] are expected to be
           // valid environment entries, but exceptions have been seen
           // (e.g., an entry of just '=' has been seen on OS/X).
           // Invalid entries (lines without a '=' or with an empty name)
           // are discarded.
-          var equalsIndex = str.indexOf('=');
+          var equalsIndex = text.indexOf('=');
           if (equalsIndex > 0) {
-            result[str.substring(0, equalsIndex)] =
-                str.substring(equalsIndex + 1);
+            result[text.substring(0, equalsIndex)] =
+                text.substring(equalsIndex + 1);
           }
         }
         _environmentCache = new UnmodifiableMapView<String, String>(result);