diff --git a/src/ssn/bencodeParser.ts b/src/ssn/bencodeParser.ts
index 223377c..37aefc1 100644
--- a/src/ssn/bencodeParser.ts
+++ b/src/ssn/bencodeParser.ts
@@ -9,7 +9,7 @@ const Decoder = new TextDecoder('utf-8');
 /** Takes a Bencoded-encoded file, parses it at the given starting position and returns a JSON object, or rejects on error. */
 function bpParse(dv: DataView, posIn: number = 0): { obj: any, pos: number } {
   let pos = posIn;
-  let obj;
+  let obj: any;
   const header = dv.getUint8(pos); pos += 1;
   switch (header) {
     case 0x64: { //'d' - dictionary (key-value object)
@@ -18,6 +18,9 @@ function bpParse(dv: DataView, posIn: number = 0): { obj: any, pos: number } {
         //read key
         const out1 = bpParse(dv, pos);
         pos = out1.pos;
+        if (typeof out1.obj !== 'string') {
+          throw new Error(`Expected dictionary key to be string but it is "${typeof out1.obj}"`);
+        }
         //read value
         const out2 = bpParse(dv, pos);
         pos = out2.pos;