diff --git a/src/riven/tbmp.rs b/src/riven/tbmp.rs
index 36a3099..24ce6d4 100644
--- a/src/riven/tbmp.rs
+++ b/src/riven/tbmp.rs
@@ -199,13 +199,15 @@ where
                             // (-m is given in pixels)
                             m &= 0x0f;
                             c += 1;
+                            out.reserve(2);
                             let &a = out
                                 .get(out.len() - 2)
                                 .ok_or_else(invalid_err)?;
+                            out.push(a);
                             let &b = out
                                 .get(out.len() - m as usize)
                                 .ok_or_else(invalid_err)?;
-                            out.extend_from_slice(&[a, b]);
+                            out.push(b);
                         },
                         [mut x @ 0x20...0x2f, ..] => {
                             // repeat last duplet, but add x to second
@@ -267,10 +269,12 @@ where
                             // output p, then pixel at -m
                             m &= 0x07;
                             c += 2;
+                            out.reserve(2);
+                            out.push(p);
                             let &b = out
                                 .get(out.len() - m as usize)
                                 .ok_or_else(invalid_err)?;
-                            out.extend_from_slice(&[p, b]);
+                            out.push(b);
                         },
                         [mut x @ 0x60...0x6f, p, ..] => {
                             // output p, then (second pixel last duplet) + x
@@ -413,9 +417,7 @@ where
                             // what remains are ugly repeat commands
                             if cmd & 0xa0 != 0xa0 || cmd & 0x0c == 0 {
                                 // this is note one of them
-                                // return Err(MhkError::InvalidFormat("unknown tBMP riven subcommand")),
-                                println!("found subcommand: {:x?}", cmds[c]);
-                                break 'decode;
+                                return Err(MhkError::InvalidFormat("unknown tBMP riven subcommand"));
                             }

                             // decode x