Index: flang/include/flang/Semantics/scope.h
===================================================================
--- flang/include/flang/Semantics/scope.h
+++ flang/include/flang/Semantics/scope.h
@@ -169,7 +169,7 @@
   mapType &commonBlocks() { return commonBlocks_; }
   const mapType &commonBlocks() const { return commonBlocks_; }
   Symbol &MakeCommonBlock(const SourceName &);
-  Symbol *FindCommonBlock(const SourceName &);
+  Symbol *FindCommonBlock(const SourceName &) const;
 
   /// Make a Symbol but don't add it to the scope.
   template <typename D>
Index: flang/lib/Semantics/scope.cpp
===================================================================
--- flang/lib/Semantics/scope.cpp
+++ flang/lib/Semantics/scope.cpp
@@ -149,7 +149,7 @@
     return symbol;
   }
 }
-Symbol *Scope::FindCommonBlock(const SourceName &name) {
+Symbol *Scope::FindCommonBlock(const SourceName &name) const {
   const auto it{commonBlocks_.find(name)};
   return it != commonBlocks_.end() ? &*it->second : nullptr;
 }