diff --git a/platform/chromium/vapi-client.js b/platform/chromium/vapi-client.js
index 0ffe987..ccfbc16 100644
--- a/platform/chromium/vapi-client.js
+++ b/platform/chromium/vapi-client.js
@@ -30,7 +30,7 @@
 /******************************************************************************/
 
 // https://bugs.chromium.org/p/project-zero/issues/detail?id=1225&desc=6#c10
-if ( !self.vAPI || !self.vAPI.uMatrix ) {
+if ( self.vAPI === undefined || self.vAPI.uMatrix !== true ) {
     self.vAPI = { uMatrix: true };
 }
 
diff --git a/platform/chromium/vapi-common.js b/platform/chromium/vapi-common.js
index f9f234a..e6a3a70 100644
--- a/platform/chromium/vapi-common.js
+++ b/platform/chromium/vapi-common.js
@@ -31,7 +31,7 @@
 /******************************************************************************/
 
 // https://bugs.chromium.org/p/project-zero/issues/detail?id=1225&desc=6#c10
-if ( !self.vAPI || !self.vAPI.uMatrix ) {
+if ( self.vAPI === undefined || self.vAPI.uMatrix !== true ) {
     self.vAPI = { uMatrix: true };
 }
 
diff --git a/platform/firefox/vapi-client.js b/platform/firefox/vapi-client.js
index 65fccb0..c101e32 100644
--- a/platform/firefox/vapi-client.js
+++ b/platform/firefox/vapi-client.js
@@ -33,7 +33,7 @@
 /******************************************************************************/
 
 // https://bugs.chromium.org/p/project-zero/issues/detail?id=1225&desc=6#c10
-if ( !self.vAPI || !self.vAPI.uMatrix ) {
+if ( self.vAPI === undefined || self.vAPI.uMatrix !== true ) {
     self.vAPI = { uMatrix: true };
 }
 
diff --git a/platform/firefox/vapi-common.js b/platform/firefox/vapi-common.js
index 994045b..4d6f9e2 100644
--- a/platform/firefox/vapi-common.js
+++ b/platform/firefox/vapi-common.js
@@ -37,7 +37,7 @@ const {Services} = Components.utils.import(
 );
 
 // https://bugs.chromium.org/p/project-zero/issues/detail?id=1225&desc=6#c10
-if ( !self.vAPI || !self.vAPI.uMatrix ) {
+if ( self.vAPI === undefined || self.vAPI.uMatrix !== true ) {
     self.vAPI = { uMatrix: true };
 }