diff --git a/lib/codemirror.css b/lib/codemirror.css
index 913a1a9c3d9ddb2a7991f326b5c38924fd7cbabc..bab16bc2c97846979811cad3e0f777e9fba53b79 100644
--- a/lib/codemirror.css
+++ b/lib/codemirror.css
@@ -166,7 +166,7 @@ div.CodeMirror span.CodeMirror-nonmatchingbracket {color: #f22;}
 }
 .CodeMirror pre {
   /* Reset some styles that the rest of the page might have set */
-  -moz-border-radius: 0; -webkit-border-radius: 0; -o-border-radius: 0; border-radius: 0;
+  -moz-border-radius: 0; -webkit-border-radius: 0; border-radius: 0;
   border-width: 0;
   background: transparent;
   font-family: inherit;
diff --git a/theme/ambiance-mobile.css b/theme/ambiance-mobile.css
index 35b3750c1b3795b11e38f906d5a32a41462cc911..88d332e1a79c7d763701d2331d33bbc3c5d5301a 100644
--- a/theme/ambiance-mobile.css
+++ b/theme/ambiance-mobile.css
@@ -1,6 +1,5 @@
 .cm-s-ambiance.CodeMirror {
   -webkit-box-shadow: none;
   -moz-box-shadow: none;
-  -o-box-shadow: none;
   box-shadow: none;
 }
diff --git a/theme/ambiance.css b/theme/ambiance.css
index beec553851a9788de14dbea06ca21f6abc12adf6..0185426f0159cc306d418c06ab5b46921e4caa10 100644
--- a/theme/ambiance.css
+++ b/theme/ambiance.css
@@ -46,7 +46,6 @@
   background-color: #202020;
   -webkit-box-shadow: inset 0 0 10px black;
   -moz-box-shadow: inset 0 0 10px black;
-  -o-box-shadow: inset 0 0 10px black;
   box-shadow: inset 0 0 10px black;
 }