1 files changed, 7 insertions, 4 deletions
diff --git a/common/nextpnr.cc b/common/nextpnr.cc
index 0b1008ac..dbe2a6f7 100644
--- a/common/nextpnr.cc
+++ b/common/nextpnr.cc
@@ -23,7 +23,7 @@ NEXTPNR_NAMESPACE_BEGIN
 
 Context *IdString::global_ctx = nullptr;
 
-void IdString::set(Context *ctx, const std::string &s)
+void IdString::set(const Context *ctx, const std::string &s)
 {
     auto it = ctx->idstring_str_to_idx->find(s);
     if (it == ctx->idstring_str_to_idx->end()) {
@@ -35,14 +35,17 @@ void IdString::set(Context *ctx, const std::string &s)
     }
 }
 
-const std::string &IdString::str(Context *ctx) const
+const std::string &IdString::str(const Context *ctx) const
 {
     return *ctx->idstring_idx_to_str->at(index);
 }
 
-const char *IdString::c_str(Context *ctx) const { return str(ctx).c_str(); }
+const char *IdString::c_str(const Context *ctx) const
+{
+    return str(ctx).c_str();
+}
 
-void IdString::initialize_add(Context *ctx, const char *s, int idx)
+void IdString::initialize_add(const Context *ctx, const char *s, int idx)
 {
     assert(ctx->idstring_str_to_idx->count(s) == 0);
     assert(int(ctx->idstring_idx_to_str->size()) == idx);