diff --git a/lib/helpers/progressEventReducer.js b/lib/helpers/progressEventReducer.js
index 85f109b7..e2c15c0d 100644
--- a/lib/helpers/progressEventReducer.js
+++ b/lib/helpers/progressEventReducer.js
@@ -7,6 +7,9 @@ export const progressEventReducer = (listener, isDownloadStream, freq = 3) => {
   const _speedometer = speedometer(50, 250);
 
   return throttle((e) => {
+    if (!e || typeof e.loaded !== 'number') {
+      return;
+    }
     const rawLoaded = e.loaded;
     const total = e.lengthComputable ? e.total : undefined;
     const loaded = total != null ? Math.min(rawLoaded, total) : rawLoaded;
diff --git a/tests/unit/helpers/progressEventReducer.test.js b/tests/unit/helpers/progressEventReducer.test.js
index 1569bee9..325347a3 100644
--- a/tests/unit/helpers/progressEventReducer.test.js
+++ b/tests/unit/helpers/progressEventReducer.test.js
@@ -24,4 +24,27 @@ describe('helpers::progressEventReducer', () => {
     expect(last.upload).toBe(true);
     expect(last.bytes).toBe(20);
   });
+
+  it('should ignore malformed events that lack a numeric loaded value', () => {
+    const events = [];
+    const [onProgress, flush] = progressEventReducer((data) => {
+      events.push(data);
+    }, false, Number.POSITIVE_INFINITY);
+
+    onProgress(undefined);
+    onProgress(null);
+    onProgress({});
+    onProgress({ loaded: null, total: 100, lengthComputable: true });
+    onProgress({ loaded: 'abc', total: 100, lengthComputable: true });
+    flush();
+
+    expect(events.length).toBe(0);
+
+    onProgress({ lengthComputable: true, loaded: 50, total: 100 });
+    flush();
+
+    expect(events.length).toBe(1);
+    expect(events[0].loaded).toBe(50);
+    expect(events[0].bytes).toBe(50);
+  });
 });