diff --git a/lib/ASTGen/Sources/ASTGen/Decls.swift b/lib/ASTGen/Sources/ASTGen/Decls.swift
index 17c7bae0e73..62e275dac7d 100644
--- a/lib/ASTGen/Sources/ASTGen/Decls.swift
+++ b/lib/ASTGen/Sources/ASTGen/Decls.swift
@@ -393,6 +393,12 @@ extension ASTGenVisitor {
       return .modify
     case .`init`:
       return .`init`
+    case .read:
+      precondition(ctx.langOptsHasFeature(.CoroutineAccessors), "(compiler bug) 'read' accessor should only be parsed with 'CoroutineAccessors' feature")
+      return .read2
+    case .modify:
+      precondition(ctx.langOptsHasFeature(.CoroutineAccessors), "(compiler bug) 'modify' accessor should only be parsed with 'CoroutineAccessors' feature")
+      return .modify2
     default:
       self.diagnose(.unknownAccessorSpecifier(specifier))
       return nil
diff --git a/test/ASTGen/decls.swift b/test/ASTGen/decls.swift
index 53a483ffcf5..afa080b51c8 100644
--- a/test/ASTGen/decls.swift
+++ b/test/ASTGen/decls.swift
@@ -1,17 +1,20 @@
 
 // RUN: %empty-directory(%t)
 // RUN: %target-swift-frontend-dump-parse -disable-availability-checking -enable-experimental-move-only -enable-experimental-concurrency -enable-experimental-feature ParserASTGen \
+// RUN:    -enable-experimental-feature CoroutineAccessors \
 // RUN:    | %sanitize-address > %t/astgen.ast
 // RUN: %target-swift-frontend-dump-parse -disable-availability-checking -enable-experimental-move-only -enable-experimental-concurrency \
+// RUN:    -enable-experimental-feature CoroutineAccessors \
 // RUN:    | %sanitize-address > %t/cpp-parser.ast
 
 // RUN: %diff -u %t/astgen.ast %t/cpp-parser.ast
 
-// RUN: %target-run-simple-swift(-Xfrontend -disable-availability-checking -Xfrontend -enable-experimental-concurrency -enable-experimental-feature ParserASTGen)
+// RUN: %target-run-simple-swift(-Xfrontend -disable-availability-checking -Xfrontend -enable-experimental-concurrency -enable-experimental-feature CoroutineAccessors -enable-experimental-feature ParserASTGen)
 
 // REQUIRES: executable_test
 // REQUIRES: swift_swift_parser
 // REQUIRES: swift_feature_ParserASTGen
+// REQUIRES: swift_feature_CoroutineAccessors
 
 // rdar://116686158
 // UNSUPPORTED: asan
@@ -108,6 +111,10 @@ func testVars() {
   var s: Int {
     get async throws { return 0 }
   }
+  var t: Int {
+    read { yield q }
+    modify { yield &q }
+  }
 }
 
 func rethrowingFn(fn: () throws -> Void) rethrows {}