diff --git a/src/usages_clang.cpp b/src/usages_clang.cpp
index 1e2193f..03d43ac 100644
--- a/src/usages_clang.cpp
+++ b/src/usages_clang.cpp
@@ -27,7 +27,7 @@ std::map<boost::filesystem::path, Usages::Clang::Cache> Usages::Clang::caches;
 Mutex Usages::Clang::caches_mutex;
 std::atomic<size_t> Usages::Clang::cache_in_progress_count(0);
 
-bool Usages::Clang::Cache::Cursor::operator==(const Cursor &o) {
+bool Usages::Clang::Cache::Cursor::operator==(const Cursor &o) const {
   for(auto &usr : usrs) {
     if(clangmm::Cursor::is_similar_kind(o.kind, kind) && o.usrs.count(usr))
       return true;
diff --git a/src/usages_clang.hpp b/src/usages_clang.hpp
index 6010d23..8b4e6a8 100644
--- a/src/usages_clang.hpp
+++ b/src/usages_clang.hpp
@@ -64,7 +64,7 @@ namespace Usages {
         clangmm::Cursor::Kind kind;
         std::unordered_set<std::string> usrs;
 
-        bool operator==(const Cursor &o);
+        bool operator==(const Cursor &o) const;
       };
 
       class Token {