diff --git a/core/commands/block.go b/core/commands/block.go
index c1b20a1bebf..282b40a7357 100644
--- a/core/commands/block.go
+++ b/core/commands/block.go
@@ -16,6 +16,8 @@ import (
 	blocks "gx/ipfs/QmYsEQydGrsxNZfAiskvQ76N2xE9hDQtSAkRSynwMiUK3c/go-block-format"
 	"gx/ipfs/QmceUdzxkimdYsgtX733uNgzf1DLHyBKN6ehGSp85ayppM/go-ipfs-cmdkit"
 	cid "gx/ipfs/QmeSrf6pzut73u6zLQkRFQ3ygt3k6XFT2kjdYP8Tnkwwyg/go-cid"
+
+	"github.com/pkg/errors"
 )
 
 type BlockStat struct {
@@ -157,27 +159,32 @@ It reads from stdin, and <key> is a base58 encoded multihash.
 			return
 		}
 
+		mhtype, _ := req.Options["mhtype"].(string)
+		mhtval, ok := mh.Names[mhtype]
+		if !ok {
+			err := fmt.Errorf("unrecognized multihash function: %s", mhtype)
+			res.SetError(err, cmdkit.ErrNormal)
+			return
+		}
+
 		var pref cid.Prefix
 		pref.Version = 1
 
-		format, _ := req.Options["format"].(string)
+		format, userFormat := req.Options["format"].(string)
 		formatval, ok := cid.Codecs[format]
 		if !ok {
 			res.SetError(fmt.Errorf("unrecognized format: %s", format), cmdkit.ErrNormal)
 			return
 		}
-		if format == "v0" {
+		if format == "v0" && (mhtval == mh.SHA2_256 || userFormat) {
 			pref.Version = 0
 		}
-		pref.Codec = formatval
-
-		mhtype, _ := req.Options["mhtype"].(string)
-		mhtval, ok := mh.Names[mhtype]
-		if !ok {
-			err := fmt.Errorf("unrecognized multihash function: %s", mhtype)
-			res.SetError(err, cmdkit.ErrNormal)
+		if mhtval != mh.SHA2_256 && pref.Version == 0 {
+			res.SetError(errors.New("cannot generate CIDv0 with non-sha256 hash function"), cmdkit.ErrNormal)
 			return
 		}
+
+		pref.Codec = formatval
 		pref.MhType = mhtval
 
 		mhlen, ok := req.Options["mhlen"].(int)
diff --git a/test/sharness/t0050-block.sh b/test/sharness/t0050-block.sh
index 285d8ad94b5..0cdd2498ba4 100755
--- a/test/sharness/t0050-block.sh
+++ b/test/sharness/t0050-block.sh
@@ -209,4 +209,16 @@ test_expect_success "no panic in output" '
   test_expect_code 1 grep "panic" stat_out
 '
 
+test_expect_success "can set multihash type and length on block put without format" '
+  HASH=$(echo "foooo" | ipfs block put --mhtype=sha3 --mhlen=16)
+'
+
+test_expect_success "output looks good" '
+  test "z2APJNN6rqZTWPpv7gYFHzh7ZEDX" = "$HASH"
+'
+
+test_expect_success "put with sha3 and cidv0 fails" '
+  echo "foooo" | test_must_fail ipfs block put --mhtype=sha3 --mhlen=16 --format=v0
+'
+
 test_done