diff --git a/platform/chromium/manifest.json b/platform/chromium/manifest.json
index 5178890b4..7ae0a06db 100644
--- a/platform/chromium/manifest.json
+++ b/platform/chromium/manifest.json
@@ -2,7 +2,7 @@
     "manifest_version": 2,
 
     "name": "uBlock Origin",
-    "version": "1.5.5",
+    "version": "1.5.6",
 
     "default_locale": "en",
     "description": "__MSG_extShortDesc__",
diff --git a/platform/chromium/vapi-client.js b/platform/chromium/vapi-client.js
index 5b9d3bc6a..55f658f0c 100644
--- a/platform/chromium/vapi-client.js
+++ b/platform/chromium/vapi-client.js
@@ -32,7 +32,7 @@
 // https://github.com/gorhill/uBlock/issues/1124
 // Looks like `contentType` is on track to be standardized:
 //   https://dom.spec.whatwg.org/#concept-document-content-type
-if ( (document.contentType || '').startsWith('image/') ) {
+if ( (document.contentType || '').lastIndexOf('image/', 0) === 0 ) {
     return; 
 }
 
diff --git a/platform/opera/manifest.json b/platform/opera/manifest.json
index 5aa15694d..a6a232cf5 100644
--- a/platform/opera/manifest.json
+++ b/platform/opera/manifest.json
@@ -2,7 +2,7 @@
     "manifest_version": 2,
 
     "name": "uBlock Origin",
-    "version": "1.5.5",
+    "version": "1.5.6",
 
     "default_locale": "en",
     "description": "__MSG_extShortDesc__",