diff --git a/src/ssn/readSolidpkg.ts b/src/ssn/readSolidpkg.ts
index f475008..2e1f525 100644
--- a/src/ssn/readSolidpkg.ts
+++ b/src/ssn/readSolidpkg.ts
@@ -1,8 +1,8 @@
 import { TextDecoder } from 'util';
 import modifyPassword from './modifyPassword';
 
-const MAGIC_END_OF_CENTRAL_DIR = 0x06054b50;
-const MAGIC_CENTRAL_DIR = 0x02014b50;
+const SIGNATURE_END_OF_CENTRAL_DIR = 0x06054b50;
+const SIGNATURE_CENTRAL_DIR = 0x02014b50;
 const COMPRESSION_DEFLATE = 8;
 
 const Decoder = new TextDecoder('utf-8');
@@ -17,7 +17,7 @@ export default function readSolidpkg(buffer: Buffer) {
   let pos = buffer.length - 22; //end of central dir is at least 22 bytes long
 
   //Find end of central dir
-  while (pos >= 0 && dv.getUint32(pos, true) !== MAGIC_END_OF_CENTRAL_DIR) {
+  while (pos >= 0 && dv.getUint32(pos, true) !== SIGNATURE_END_OF_CENTRAL_DIR) {
     pos -= 1;
   }
   if (pos < 0) {
@@ -25,7 +25,11 @@ export default function readSolidpkg(buffer: Buffer) {
   }
   pos += 4;
 
-  //skip 6 bytes
+  /** skip 6 bytes:
+   * number of this disk,
+   * number of the disk with the start of the central directory
+   * total number of entries in the central directory on this disk
+   */
   pos += 6;
 
   /** Total number of entries in the central directory */
@@ -34,6 +38,7 @@ export default function readSolidpkg(buffer: Buffer) {
   const centralDirSize = dv.getUint32(pos, true); pos += 4;
   /** Offset of start of central directory with respect to the starting disk number */
   const centralDirOffset = dv.getUint32(pos, true); pos += 4;
+  //ignore .ZIP file comment length
 
   if (numEntries !== 1) {
     throw new Error(`Expected numEntries == 1 in end of central dir but it was "${numEntries}"`);
@@ -51,9 +56,9 @@ export default function readSolidpkg(buffer: Buffer) {
   pos -= 20 + centralDirSize;
 
   {
-    const magicNum = dv.getUint32(pos, true); pos += 4;
-    if (magicNum !== MAGIC_CENTRAL_DIR) {
-      throw new Error(`Expected central dir signature but found "0x${magicNum.toString(16)}"`);
+    const signature = dv.getUint32(pos, true); pos += 4;
+    if (signature !== SIGNATURE_CENTRAL_DIR) {
+      throw new Error(`Expected central dir signature but found "0x${signature.toString(16)}"`);
     }
   }
 
@@ -82,6 +87,9 @@ export default function readSolidpkg(buffer: Buffer) {
   pos += 8; //skip disk num start and file attributes
   const relOffset = dv.getUint32(pos, true); pos += 4;
   const fileName = Decoder.decode(new DataView(arrayBuffer, pos, fileNameLength)); pos += fileNameLength; //skip file name
+  if (fileName !== 'metafile.solid') {
+    throw new Error(`Expected file name to be "metafile.solid" but it was "${fileName}".`);
+  }
 
   //read password from extra field
   let encodedPassword: Uint8Array | undefined;