diff --git a/include/sirit/sirit.h b/include/sirit/sirit.h
index 574a9cc..c26304b 100644
--- a/include/sirit/sirit.h
+++ b/include/sirit/sirit.h
@@ -242,6 +242,9 @@ public:
         return OpFunctionCall(result_type, function, std::span<const Id>({arguments...}));
     }
 
+    /// Declare a formal parameter of the current function.
+    Id OpFunctionParameter(Id result_type);
+
     // Flow
 
     /**
diff --git a/src/instructions/function.cpp b/src/instructions/function.cpp
index ece60e6..f84cd7f 100644
--- a/src/instructions/function.cpp
+++ b/src/instructions/function.cpp
@@ -26,4 +26,9 @@ Id Module::OpFunctionCall(Id result_type, Id function, std::span<const Id> argum
     return *code << OpId{spv::Op::OpFunctionCall, result_type} << function << arguments << EndOp{};
 }
 
+Id Module::OpFunctionParameter(Id result_type) {
+    code->Reserve(3);
+    return *code << OpId{spv::Op::OpFunctionParameter, result_type} << EndOp{};
+}
+
 } // namespace Sirit