diff --git a/src/V3MemberMap.h b/src/V3MemberMap.h
index 6f6c8f008..8601214ca 100644
--- a/src/V3MemberMap.h
+++ b/src/V3MemberMap.h
@@ -35,12 +35,12 @@
 class VMemberMap final {
     // MEMBERS
     using MemberMap = std::map<std::string, AstNode*>;
-    using NodeMap = std::map<AstNode*, MemberMap>;
+    using NodeMap = std::map<const AstNode*, MemberMap>;
     NodeMap m_map;  // Map of nodes being tracked
 public:
     void clear() { m_map.clear(); }
     // Find 'name' under 'nodep', caching nodep's children if needed
-    AstNode* findMember(AstNode* nodep, const std::string& name) {
+    AstNode* findMember(const AstNode* nodep, const std::string& name) {
         auto nit = m_map.find(nodep);
         if (VL_UNLIKELY(nit == m_map.end())) {
             scan(nodep);
@@ -51,7 +51,7 @@ public:
         return mit->second;
     }
     // Insert under the given parent node the child's name
-    void insert(AstNode* nodep, AstNode* childp) {
+    void insert(const AstNode* nodep, AstNode* childp) {
         auto nit = m_map.find(nodep);
         if (nit == m_map.end()) {
             scan(nodep);
@@ -61,10 +61,10 @@ public:
     }
 
 private:
-    void scan(AstNode* nodep) {
+    void scan(const AstNode* nodep) {
         const auto nitPair = m_map.emplace(nodep, MemberMap{});
         MemberMap& mmapr = nitPair.first->second;
-        if (AstClass* const anodep = VN_CAST(nodep, Class)) {
+        if (const AstClass* const anodep = VN_CAST(nodep, Class)) {
             for (AstNode* itemp = anodep->membersp(); itemp; itemp = itemp->nextp()) {
                 if (const AstScope* const scopep = VN_CAST(itemp, Scope)) {
                     for (AstNode* blockp = scopep->blocksp(); blockp; blockp = blockp->nextp()) {
@@ -74,7 +74,8 @@ private:
                     if (AstClass::isCacheableChild(itemp)) memberInsert(mmapr, itemp);
                 }
             }
-        } else if (AstNodeUOrStructDType* const anodep = VN_CAST(nodep, NodeUOrStructDType)) {
+        } else if (const AstNodeUOrStructDType* const anodep
+                   = VN_CAST(nodep, NodeUOrStructDType)) {
             for (AstNode* itemp = anodep->membersp(); itemp; itemp = itemp->nextp()) {
                 memberInsert(mmapr, itemp);
             }