3 files changed, 20 insertions, 5 deletions
diff --git a/src/nvim/eval.lua b/src/nvim/eval.lua
index a7242ba73a..5f355abe3c 100644
--- a/src/nvim/eval.lua
+++ b/src/nvim/eval.lua
@@ -250,7 +250,7 @@ return {
     min={args=1, base=1},
     mkdir={args={1, 3}},
     mode={args={0, 1}},
-    msgpackdump={args=1},
+    msgpackdump={args={1, 2}},
     msgpackparse={args=1},
     nextnonblank={args=1},
     nr2char={args={1, 2}},
diff --git a/src/nvim/eval/encode.c b/src/nvim/eval/encode.c
index 1c2274c410..b5e50e7ef5 100644
--- a/src/nvim/eval/encode.c
+++ b/src/nvim/eval/encode.c
@@ -47,6 +47,14 @@ const char *const encode_special_var_names[] = {
 # include "eval/encode.c.generated.h"
 #endif
 
+/// Msgpack callback for writing to a Blob
+int encode_blob_write(void *const data, const char *const buf, const size_t len)
+  FUNC_ATTR_NONNULL_ARG(1)
+{
+  ga_concat_len(&((blob_T *)data)->bv_ga, buf, len);
+  return (int)len;
+}
+
 /// Msgpack callback for writing to readfile()-style list
 int encode_list_write(void *const data, const char *const buf, const size_t len)
   FUNC_ATTR_NONNULL_ARG(1)
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index e83e0ac0cc..a2ea74b19b 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -6506,9 +6506,16 @@ static void f_msgpackdump(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     EMSG2(_(e_listarg), "msgpackdump()");
     return;
   }
-  list_T *const ret_list = tv_list_alloc_ret(rettv, kListLenMayKnow);
   list_T *const list = argvars[0].vval.v_list;
-  msgpack_packer *lpacker = msgpack_packer_new(ret_list, &encode_list_write);
+  msgpack_packer *packer;
+  if (argvars[1].v_type != VAR_UNKNOWN
+      && strequal(tv_get_string(&argvars[1]), "B")) {
+    tv_blob_alloc_ret(rettv);
+    packer = msgpack_packer_new(rettv->vval.v_blob, &encode_blob_write);
+  } else {
+    packer = msgpack_packer_new(tv_list_alloc_ret(rettv, kListLenMayKnow),
+                                &encode_list_write);
+  }
   const char *const msg = _("msgpackdump() argument, index %i");
   // Assume that translation will not take more then 4 times more space
   char msgbuf[sizeof("msgpackdump() argument, index ") * 4 + NUMBUFLEN];
@@ -6516,11 +6523,11 @@ static void f_msgpackdump(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   TV_LIST_ITER(list, li, {
     vim_snprintf(msgbuf, sizeof(msgbuf), (char *)msg, idx);
     idx++;
-    if (encode_vim_to_msgpack(lpacker, TV_LIST_ITEM_TV(li), msgbuf) == FAIL) {
+    if (encode_vim_to_msgpack(packer, TV_LIST_ITEM_TV(li), msgbuf) == FAIL) {
       break;
     }
   });
-  msgpack_packer_free(lpacker);
+  msgpack_packer_free(packer);
 }
 
 /// "msgpackparse" function