diff --git a/cid.go b/cid.go
index ae3d1fd..cc7c4b1 100644
--- a/cid.go
+++ b/cid.go
@@ -727,6 +727,10 @@ func CidFromReader(r io.Reader) (int, Cid, error) {
 	// The varint package wants a io.ByteReader, so we must wrap our io.Reader.
 	vers, err := varint.ReadUvarint(br)
 	if err != nil {
+		if err == io.EOF {
+			// No data; not an invalid CID.
+			return 0, Undef, err
+		}
 		return len(br.dst), Undef, ErrInvalidCid{err}
 	}
 
diff --git a/cid_test.go b/cid_test.go
index 31989da..f0c6ad5 100644
--- a/cid_test.go
+++ b/cid_test.go
@@ -783,6 +783,20 @@ func TestBadCidInput(t *testing.T) {
 	}
 }
 
+func TestFromReaderNoData(t *testing.T) {
+	// Reading no data from io.Reader should return io.EOF, not ErrInvalidCid.
+	n, cid, err := CidFromReader(bytes.NewReader(nil))
+	if err != io.EOF {
+		t.Fatal("Expected io.EOF error")
+	}
+	if cid != Undef {
+		t.Fatal("Expected Undef CID")
+	}
+	if n != 0 {
+		t.Fatal("Expected 0 data")
+	}
+}
+
 func TestBadParse(t *testing.T) {
 	hash, err := mh.Sum([]byte("foobar"), mh.SHA3_256, -1)
 	if err != nil {