diff --git a/CHANGELOG b/CHANGELOG
index 50b6a2d9e..bd4feacf3 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,7 @@
 CHANGELOG Roundcube Webmail
 ===========================
 
+- Fix PDF support detection for Firefox PDF.js (#1488972)
 - Fix messages list focus issue in Internet Explorer (#1489058)
 - Add db_prefix configuration option in place of db_table_*/db_sequence_* options
 - Make possible to use db_prefix for schema initialization in Installer (#1489067)
diff --git a/program/js/app.js b/program/js/app.js
index 5d7e28640..58810c24a 100644
--- a/program/js/app.js
+++ b/program/js/app.js
@@ -6721,6 +6721,15 @@ function rcube_webmail()
         return 1;
     }
 
+    // this will detect any pdf plugin including PDF.js in Firefox
+    var obj = document.createElement('OBJECT');
+    obj.onload = function() { rcmail.env.browser_capabilities.pdf = 1; };
+    obj.onerror = function() { rcmail.env.browser_capabilities.pdf = 0; };
+    obj.style.display = 'none';
+    obj.type = 'application/pdf';
+    obj.data = 'program/resources/blank.pdf';
+    document.body.appendChild(obj);
+
     return 0;
   };
 
diff --git a/program/resources/blank.pdf b/program/resources/blank.pdf
new file mode 100644
index 000000000..7bf83e390
Binary files /dev/null and b/program/resources/blank.pdf differ