diff --git a/include/sirit/sirit.h b/include/sirit/sirit.h
index 1a0def9..71f8699 100644
--- a/include/sirit/sirit.h
+++ b/include/sirit/sirit.h
@@ -920,6 +920,15 @@ public:
     Id OpImageQuerySamples(Id result_type, Id image);
 
 private:
+    struct HashOp {
+        std::size_t operator()(const std::unique_ptr<Op>& op) const noexcept;
+    };
+
+    struct EqualOp {
+        bool operator()(const std::unique_ptr<Op>& lhs, const std::unique_ptr<Op>& rhs) const
+            noexcept;
+    };
+
     Id AddCode(std::unique_ptr<Op> op);
 
     Id AddCode(spv::Op opcode, std::optional<std::uint32_t> id = {});
@@ -945,7 +954,7 @@ private:
     std::vector<std::unique_ptr<Op>> execution_modes;
     std::vector<std::unique_ptr<Op>> debug;
     std::vector<std::unique_ptr<Op>> annotations;
-    std::unordered_set<std::unique_ptr<Op>> declarations;
+    std::unordered_set<std::unique_ptr<Op>, HashOp, EqualOp> declarations;
     std::vector<Id> sorted_declarations;
 
     std::vector<Id> global_variables;
diff --git a/src/sirit.cpp b/src/sirit.cpp
index 50135e3..f65e9a5 100644
--- a/src/sirit.cpp
+++ b/src/sirit.cpp
@@ -20,6 +20,15 @@ static void WriteSet(Stream& stream, const T& set) {
     }
 }
 
+std::size_t Module::HashOp::operator()(const std::unique_ptr<Op>& op) const noexcept {
+    return op->Hash();
+}
+
+bool Module::EqualOp::operator()(const std::unique_ptr<Op>& lhs,
+                                 const std::unique_ptr<Op>& rhs) const noexcept {
+    return *lhs == *rhs;
+}
+
 Module::Module(u32 version) : version(version) {}
 
 Module::~Module() = default;