diff --git a/loopy/preprocess.py b/loopy/preprocess.py
index 0857a5e721d72183cdfa13bf758333dd1b538952..4309f9ae1d2a5419e9b608fc34ceccb4cbe55654 100644
--- a/loopy/preprocess.py
+++ b/loopy/preprocess.py
@@ -2156,15 +2156,16 @@ def check_functions_are_scoped(kernel):
         if isinstance(insn, MultiAssignmentBase):
             unscoped_calls = UnScopedCallCollector()(subst_expander(
                 insn.expression))
+            if unscoped_calls:
+                raise LoopyError("Unknown function '%s' obtained -- register a "
+                        "function or a kernel corresponding to it." %
+                        set(unscoped_calls).pop())
         elif isinstance(insn, (CInstruction, _DataObliviousInstruction)):
             pass
         else:
             raise NotImplementedError("check_function_are_scoped not "
                     "implemented for %s type of instruction." % type(insn))
 
-        if unscoped_calls:
-            raise LoopyError("Unknown function '%s' obtained -- register a function"
-                    " or a kernel corresponding to it." % set(unscoped_calls).pop())
 
 # }}}