diff --git a/src/script_opt/CPP/Compile.h b/src/script_opt/CPP/Compile.h
index 16f9312b89..033ed4fa67 100644
--- a/src/script_opt/CPP/Compile.h
+++ b/src/script_opt/CPP/Compile.h
@@ -186,7 +186,7 @@ public:
 	// Returns a mapping of from Attr objects to their associated
 	// initialization information.  The Attr must have previously
 	// been registered.
-	auto& ProcessedAttr() { return processed_attr; }
+	auto& ProcessedAttr() const { return processed_attr; }
 
 	// True if the given expression is simple enough that we can
 	// generate code to evaluate it directly, and don't need to
diff --git a/src/script_opt/CPP/InitsInfo.cc b/src/script_opt/CPP/InitsInfo.cc
index eab425d658..f02f7f04b2 100644
--- a/src/script_opt/CPP/InitsInfo.cc
+++ b/src/script_opt/CPP/InitsInfo.cc
@@ -309,7 +309,7 @@ AttrsInfo::AttrsInfo(CPPCompile* _c, const AttributesPtr& _attrs) : CompoundItem
 	for ( const auto& a : _attrs->GetAttrs() )
 		{
 		ASSERT(c->ProcessedAttr().count(a.get()) > 0);
-		auto gi = c->ProcessedAttr()[a.get()];
+		const auto& gi = c->ProcessedAttr().at(a.get());
 		init_cohort = max(init_cohort, gi->InitCohort() + 1);
 		vals.emplace_back(Fmt(gi->Offset()));
 		}