diff --git a/artiq/compiler/validators/local_access.py b/artiq/compiler/validators/local_access.py
index ee43b30a7..c86f3e46b 100644
--- a/artiq/compiler/validators/local_access.py
+++ b/artiq/compiler/validators/local_access.py
@@ -99,12 +99,14 @@ class LocalAccessValidator:
 
                 if isinstance(insn, ir.Closure):
                     env = insn.environment()
-                    for var_name in block_state[env]:
-                        if not block_state[env][var_name]:
-                            # A closure would capture this variable while it is not always
-                            # initialized. Note that this check is transitive.
-                            self._uninitialized_access(insn, var_name,
-                                                       pred_at_fault(env, var_name))
+                    # Make sure this environment has any interesting variables.
+                    if env in block_state:
+                        for var_name in block_state[env]:
+                            if not block_state[env][var_name]:
+                                # A closure would capture this variable while it is not always
+                                # initialized. Note that this check is transitive.
+                                self._uninitialized_access(insn, var_name,
+                                                           pred_at_fault(env, var_name))
 
             # Save the state.
             state[block] = block_state