diff --git a/src/Compilers/CSharp/Portable/Binder/Binder_Await.cs b/src/Compilers/CSharp/Portable/Binder/Binder_Await.cs
index 7ac46015217f6..ef9417f95605e 100644
--- a/src/Compilers/CSharp/Portable/Binder/Binder_Await.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Binder_Await.cs
@@ -185,9 +185,21 @@ private bool ReportBadAwaitWithoutAsync(SyntaxNodeOrToken nodeOrToken, BindingDi
                         }
                         else
                         {
-                            info = method.ReturnsVoid ?
-                                new CSDiagnosticInfo(ErrorCode.ERR_BadAwaitWithoutVoidAsyncMethod) :
-                                new CSDiagnosticInfo(ErrorCode.ERR_BadAwaitWithoutAsyncMethod, method.ReturnType);
+                            if (method.ReturnsVoid)
+                            {
+                                info = new CSDiagnosticInfo(ErrorCode.ERR_BadAwaitWithoutVoidAsyncMethod);
+                            }
+                            else if (method.IsIterator && InMethodBinder.IsAsyncStreamInterface(Compilation, method.RefKind, method.ReturnType))
+                            {
+                                // For async iterators, we don't report an error on await because ERR_IteratorMustBeAsync
+                                // is already reported by ExecutableCodeBinder.ValidateIteratorMethod, which tells the user to add 'async'.
+                                // Reporting a second error here would be redundant.
+                                return false;
+                            }
+                            else
+                            {
+                                info = new CSDiagnosticInfo(ErrorCode.ERR_BadAwaitWithoutAsyncMethod, method.ReturnType);
+                            }
                         }
                         break;
                 }
diff --git a/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncIteratorTests.cs b/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncIteratorTests.cs
index e0e1ebe77a8be..ee2351156ea27 100644
--- a/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncIteratorTests.cs
+++ b/src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenAsyncIteratorTests.cs
@@ -1996,13 +1996,28 @@ static System.Collections.Generic.IAsyncEnumerator<int> M(int value)
             comp.VerifyDiagnostics(
                 // (4,61): error CS8403: Method 'C.M(int)' with an iterator block must be 'async' to return 'IAsyncEnumerator<int>'
                 //     static System.Collections.Generic.IAsyncEnumerator<int> M(int value)
-                Diagnostic(ErrorCode.ERR_IteratorMustBeAsync, "M").WithArguments("C.M(int)", "System.Collections.Generic.IAsyncEnumerator<int>").WithLocation(4, 61),
-                // (7,9): error CS4032: The 'await' operator can only be used within an async method. Consider marking this method with the 'async' modifier and changing its return type to 'Task<IAsyncEnumerator<int>>'.
-                //         await System.Threading.Tasks.Task.CompletedTask;
-                Diagnostic(ErrorCode.ERR_BadAwaitWithoutAsyncMethod, "await System.Threading.Tasks.Task.CompletedTask").WithArguments("System.Collections.Generic.IAsyncEnumerator<int>").WithLocation(7, 9)
+                Diagnostic(ErrorCode.ERR_IteratorMustBeAsync, "M").WithArguments("C.M(int)", "System.Collections.Generic.IAsyncEnumerator<int>").WithLocation(4, 61)
                 );
+        }
 
-            // This error message is rather poor. Tracked by https://github.com/dotnet/roslyn/issues/31113
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/31113")]
+        public void AsyncIteratorReturningEnumerable_WithoutAsync()
+        {
+            string source = """
+                class C
+                {
+                    static System.Collections.Generic.IAsyncEnumerable<int> M(int value)
+                    {
+                        yield return value;
+                        await System.Threading.Tasks.Task.CompletedTask;
+                    }
+                }
+                """;
+            var comp = CreateCompilationWithAsyncIterator(source);
+            comp.VerifyDiagnostics(
+                // (3,61): error CS8403: Method 'C.M(int)' with an iterator block must be 'async' to return 'IAsyncEnumerable<int>'
+                //     static System.Collections.Generic.IAsyncEnumerable<int> M(int value)
+                Diagnostic(ErrorCode.ERR_IteratorMustBeAsync, "M").WithArguments("C.M(int)", "System.Collections.Generic.IAsyncEnumerable<int>").WithLocation(3, 61));
         }
 
         [Fact]