diff --git a/src/support.js b/src/support.js
index 8e8d20e0..91ee77d3 100644
--- a/src/support.js
+++ b/src/support.js
@@ -40,7 +40,8 @@
 
 		// Make sure that element opacity exists
 		// (IE uses filter instead)
-		opacity: a.style.opacity === "0.55",
+		// Use a regex to work around a WebKit issue. See #5145
+		opacity: /^0.55$/.test( a.style.opacity ),
 
 		// Verify style float existence
 		// (IE uses styleFloat instead of cssFloat)