diff --git a/src/scanner.js b/src/scanner.js
index 1e2f169f..d48b1818 100644
--- a/src/scanner.js
+++ b/src/scanner.js
@@ -96,14 +96,16 @@ class Analyzer {
     this.canvas.style.display = 'none';
     this.canvasContext = null;
 
-    this.decodeCallback = ZXing.Runtime.addFunction(function (ptr, len, resultIndex, resultCount) {
-      let result = new Uint8Array(ZXing.HEAPU8.buffer, ptr, len);
-      let str = String.fromCharCode.apply(null, result);
-      if (resultIndex === 0) {
-        window.zxDecodeResult = '';
-      }
-      window.zxDecodeResult += str;
-    });
+    if(!Analyzer.decodeCallback) {
+        Analyzer.decodeCallback = ZXing.Runtime.addFunction(function (ptr, len, resultIndex, resultCount) {
+          let result = new Uint8Array(ZXing.HEAPU8.buffer, ptr, len);
+          let str = String.fromCharCode.apply(null, result);
+          if (resultIndex === 0) {
+            window.zxDecodeResult = '';
+          }
+          window.zxDecodeResult += str;
+        });
+    }
   }
 
   analyze() {
@@ -142,7 +144,7 @@ class Analyzer {
       ZXing.HEAPU8[this.imageBuffer + j] = Math.trunc((r + g + b) / 3);
     }
 
-    let err = ZXing._decode_qr(this.decodeCallback);
+    let err = ZXing._decode_qr(Analyzer.decodeCallback);
     if (err) {
       return null;
     }