diff --git a/Sources/Core/GTMSessionFetcher.m b/Sources/Core/GTMSessionFetcher.m
index e3fdf78..870a740 100644
--- a/Sources/Core/GTMSessionFetcher.m
+++ b/Sources/Core/GTMSessionFetcher.m
@@ -1686,7 +1686,7 @@ - (void)restoreDefaultStateForSessionIdentifierMetadata {
   }
 }
 
-- (nullable NSDictionary *)sessionIdentifierMetadata {
+- (nullable NSDictionary<NSString *, id> *)sessionIdentifierMetadata {
   @synchronized(self) {
     GTMSessionMonitorSynchronized(self);
 
@@ -1694,7 +1694,7 @@ - (nullable NSDictionary *)sessionIdentifierMetadata {
   }
 }
 
-- (nullable NSDictionary *)sessionIdentifierMetadataUnsynchronized {
+- (nullable NSDictionary<NSString *, id> *)sessionIdentifierMetadataUnsynchronized {
   GTMSessionCheckSynchronized(self);
 
   // Session Identifier format: "com.google.<ClassName>_<UUID>_<Metadata in JSON format>
diff --git a/Sources/Core/Public/GTMSessionFetcher/GTMSessionFetcher.h b/Sources/Core/Public/GTMSessionFetcher/GTMSessionFetcher.h
index 6c1492d..6398f6e 100644
--- a/Sources/Core/Public/GTMSessionFetcher/GTMSessionFetcher.h
+++ b/Sources/Core/Public/GTMSessionFetcher/GTMSessionFetcher.h
@@ -872,10 +872,9 @@ __deprecated_msg("implement GTMSessionFetcherAuthorizer instead")
 
 // The fetcher encodes information used to resume a session in the session identifier.
 // This method, intended for internal use returns the encoded information.  The sessionUserInfo
-// dictionary is stored as identifier metadata.
-// NOTE: This type is a lie and could be an issue for Swift. The values for private keys (prefixed
-// with an underscore) aren't always strings; but changing the type is a breaking change.
-- (nullable NSDictionary<NSString *, NSString *> *)sessionIdentifierMetadata;
+// dictionary is stored as identifier metadata. The values here are limited to things that
+// can be stored in a plist, so they aren't completely open ended.
+- (nullable NSDictionary<NSString *, id> *)sessionIdentifierMetadata;
 
 #if TARGET_OS_IPHONE && !TARGET_OS_WATCH
 // The app should pass to this method the completion handler passed in the app delegate method