diff --git a/artiq/py2llvm/typing.py b/artiq/py2llvm/typing.py
index a52041275..5e2c498fc 100644
--- a/artiq/py2llvm/typing.py
+++ b/artiq/py2llvm/typing.py
@@ -312,7 +312,6 @@ class ASTTypedRewriter(algorithm.Transformer):
     visit_Import = visit_unsupported
     visit_ImportFrom = visit_unsupported
     visit_Try = visit_unsupported
-    visit_With = visit_unsupported
 
 
 class Inferencer(algorithm.Visitor):
@@ -725,6 +724,15 @@ class Inferencer(algorithm.Visitor):
                 node.keyword_loc)
             self.engine.process(diag)
 
+    def visit_withitem(self, node):
+        self.generic_visit(node)
+        if True: # none are supported yet
+            diag = diagnostic.Diagnostic("error",
+                "value of type {type} cannot act as a context manager",
+                {"type": types.TypePrinter().name(node.context_expr.type)},
+                node.context_expr.loc)
+            self.engine.process(diag)
+
     def visit_FunctionDefT(self, node):
         old_function, self.function = self.function, node
         old_in_loop, self.in_loop = self.in_loop, False