diff --git a/src/libexpr/nix_api_value.cc b/src/libexpr/nix_api_value.cc
index ceff036c9..dae50352b 100644
--- a/src/libexpr/nix_api_value.cc
+++ b/src/libexpr/nix_api_value.cc
@@ -3,6 +3,7 @@
 #include "eval.hh"
 #include "gc/gc.h"
 #include "globals.hh"
+#include "primops.hh"
 #include "value.hh"
 
 #include "nix_api_expr.h"
@@ -55,6 +56,15 @@ PrimOp *nix_alloc_primop(nix_c_context *context, PrimOpFun fun, int arity,
   NIXC_CATCH_ERRS_NULL
 }
 
+nix_err nix_register_primop(nix_c_context *context, PrimOp *primOp) {
+  if (context)
+    context->last_err_code = NIX_OK;
+  try {
+    nix::RegisterPrimOp r(std::move(*((nix::PrimOp *)primOp)));
+  }
+  NIXC_CATCH_ERRS
+}
+
 Value *nix_alloc_value(nix_c_context *context, State *state) {
   if (context)
     context->last_err_code = NIX_OK;
diff --git a/src/libexpr/nix_api_value.h b/src/libexpr/nix_api_value.h
index 08eb34fc5..af1d211a3 100644
--- a/src/libexpr/nix_api_value.h
+++ b/src/libexpr/nix_api_value.h
@@ -88,6 +88,20 @@ typedef void (*PrimOpFun)(State *state, int pos, Value **args, Value *v);
  */
 PrimOp *nix_alloc_primop(nix_c_context *context, PrimOpFun fun, int arity,
                          const char *name, const char **args, const char *doc);
+
+/** @brief add a primop to builtins
+ *
+ * Only applies to new States.
+ *
+ * Moves your primop into the global
+ * registry, meaning your input primOp is no longer usable
+ * (but still possibly subject to garbage collection).
+ *
+ * @param[out] context Optional, stores error information
+ * @return primop, or null in case of errors
+ *
+ */
+nix_err nix_register_primop(nix_c_context *context, PrimOp *primOp);
 /** @} */
 
 // Function prototypes