diff --git a/src/nvim/api/private/converter.c b/src/nvim/api/private/converter.c
index 3159a305d8..7a1b715fef 100644
--- a/src/nvim/api/private/converter.c
+++ b/src/nvim/api/private/converter.c
@@ -76,8 +76,9 @@ static Object typval_cbuf_to_obj(EncodedData *edata, const char *data, size_t le
 
 #define TYPVAL_ENCODE_CONV_FUNC_START(tv, fun, prefix) \
   do { \
-    ufunc_T *fp = find_func(fun); \
-    if (fp != NULL && (fp->uf_flags & FC_LUAREF)) { \
+    const char *const fun_ = (fun); \
+    ufunc_T *fp; \
+    if (fun_ != NULL && (fp = find_func(fun_)) != NULL && fp->uf_flags & FC_LUAREF) { \
       kvi_push(edata->stack, LUAREF_OBJ(api_new_luaref(fp->uf_luaref))); \
     } else { \
       TYPVAL_ENCODE_CONV_NIL(tv); \
diff --git a/src/nvim/lua/converter.c b/src/nvim/lua/converter.c
index 669ad31860..f971ed5fb7 100644
--- a/src/nvim/lua/converter.c
+++ b/src/nvim/lua/converter.c
@@ -455,8 +455,9 @@ static bool typval_conv_special = false;
 
 #define TYPVAL_ENCODE_CONV_FUNC_START(tv, fun, prefix) \
   do { \
-    ufunc_T *fp = find_func(fun); \
-    if (fp != NULL && fp->uf_flags & FC_LUAREF) { \
+    const char *const fun_ = (fun); \
+    ufunc_T *fp; \
+    if (fun_ != NULL && (fp = find_func(fun_)) != NULL && fp->uf_flags & FC_LUAREF) { \
       nlua_pushref(lstate, fp->uf_luaref); \
     } else { \
       TYPVAL_ENCODE_CONV_NIL(tv); \