diff --git a/IPython/core/async_helpers.py b/IPython/core/async_helpers.py
index d334dba..fa3d5cf 100644
--- a/IPython/core/async_helpers.py
+++ b/IPython/core/async_helpers.py
@@ -80,6 +80,40 @@ def _asyncify(code: str) -> str:
     return res
 
 
+class _AsyncSyntaxErrorVisitor(ast.NodeVisitor):
+    """
+    Find syntax errors that would be an error in an async repl, but because
+    the implementation involves wrapping the repl in an async function, it
+    is erroneously allowed (e.g. yield or return at the top level)
+    """
+    def generic_visit(self, node):
+        func_types = (ast.FunctionDef, ast.AsyncFunctionDef)
+        invalid_types = (ast.Return, ast.Yield, ast.YieldFrom)
+
+        if isinstance(node, func_types):
+            return      # Don't recurse into functions
+        elif isinstance(node, invalid_types):
+            raise SyntaxError()
+        else:
+            super().generic_visit(node)
+
+
+def _async_parse_cell(cell: str) -> ast.AST:
+    """
+    This is a compatibility shim for pre-3.7 when async outside of a function
+    is a syntax error at the parse stage.
+
+    It will return an abstract syntax tree parsed as if async and await outside
+    of a function were not a syntax error.
+    """
+    if sys.version_info < (3, 7):
+        # Prior to 3.7 you need to asyncify before parse
+        wrapped_parse_tree = ast.parse(_asyncify(cell))
+        return wrapped_parse_tree.body[0].body[0]
+    else:
+        return ast.parse(cell)
+
+
 def _should_be_async(cell: str) -> bool:
     """Detect if a block of code need to be wrapped in an `async def`
 
@@ -99,8 +133,12 @@ def _should_be_async(cell: str) -> bool:
         return False
     except SyntaxError:
         try:
-            ast.parse(_asyncify(cell))
-            # TODO verify ast has not "top level" return or yield.
+            parse_tree = _async_parse_cell(cell)
+
+            # Raise a SyntaxError if there are top-level return or yields
+            v = _AsyncSyntaxErrorVisitor()
+            v.visit(parse_tree)
+
         except SyntaxError:
             return False
         return True