diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index d6243f9d01..ab1127ee99 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -13,6 +13,7 @@
 #include <script/script.h>
 #include <uint256.h>
 extern "C" {
+#include <simplicity/elements/env.h>
 #include <simplicity/elements/exec.h>
 #include <simplicity/errorCodes.h>
 }
@@ -2650,6 +2651,10 @@ void PrecomputedTransactionData::Init(const T& txTo, std::vector<CTxOut>&& spent
     }
 }
 
+void SimplicityTransactionDeleter::operator()(elementsTransaction* ptr) const {
+    simplicity_elements_freeTransaction(ptr);
+}
+
 template <class T>
 PrecomputedTransactionData::PrecomputedTransactionData(const T& txTo)
      : PrecomputedTransactionData(uint256{})
diff --git a/src/script/interpreter.h b/src/script/interpreter.h
index a9004b8f07..28c99272b6 100644
--- a/src/script/interpreter.h
+++ b/src/script/interpreter.h
@@ -9,9 +9,6 @@
 #include <consensus/amount.h>
 #include <hash.h>
 #include <primitives/transaction.h>
-extern "C" {
-#include <simplicity/elements/env.h>
-}
 #include <script/script_error.h> // IWYU pragma: export
 #include <span.h>
 #include <uint256.h>
@@ -171,12 +168,13 @@ enum : uint32_t {
 
 bool CheckSignatureEncoding(const std::vector<unsigned char> &vchSig, unsigned int flags, ScriptError* serror);
 
+// Forward declarations of Simplicity structures.
+struct elementsTransaction;
+struct rawElementsTapEnv;
+
 struct SimplicityTransactionDeleter
 {
-    void operator()(elementsTransaction* ptr)
-    {
-        simplicity_elements_freeTransaction(ptr);
-    }
+    void operator()(elementsTransaction* ptr) const;
 };
 using SimplicityTransactionUniquePtr = std::unique_ptr<elementsTransaction, SimplicityTransactionDeleter>;