diff --git a/IPython/html/static/notebook/less/codemirror.less b/IPython/html/static/notebook/less/codemirror.less
index 2bb06af..4995983 100644
--- a/IPython/html/static/notebook/less/codemirror.less
+++ b/IPython/html/static/notebook/less/codemirror.less
@@ -22,7 +22,7 @@
     overflow-x: auto;
 }
 
-@-moz-document {
+@-moz-document url-prefix() {
   /* Firefox does weird and terrible things (#3549) when overflow-x is auto */
   /* It doesn't respect the overflow setting anyway, so we can workaround it with this */
   .CodeMirror-scroll {
diff --git a/IPython/html/static/style/ipython.min.css b/IPython/html/static/style/ipython.min.css
index 0d16945..d940f33 100644
--- a/IPython/html/static/style/ipython.min.css
+++ b/IPython/html/static/style/ipython.min.css
@@ -79,7 +79,7 @@ div.input{page-break-inside:avoid;display:-webkit-box;-webkit-box-orient:horizon
 div.input_prompt{color:#000080;border-top:1px solid transparent}
 .CodeMirror{line-height:1.231em;height:auto;background:none;}
 .CodeMirror-scroll{overflow-y:hidden;overflow-x:auto}
-@-moz-document {.CodeMirror-scroll{overflow-x:hidden}}.CodeMirror-lines{padding:.4em}
+@-moz-document url-prefix(){.CodeMirror-scroll{overflow-x:hidden}}.CodeMirror-lines{padding:.4em}
 .CodeMirror-linenumber{padding:0 8px 0 4px}
 .CodeMirror-gutters{border-bottom-left-radius:4px;border-top-left-radius:4px}
 .CodeMirror pre{padding:0;border:0;-webkit-border-radius:0;-moz-border-radius:0;border-radius:0}
diff --git a/IPython/html/static/style/style.min.css b/IPython/html/static/style/style.min.css
index 6d5391e..c78ebe6 100644
--- a/IPython/html/static/style/style.min.css
+++ b/IPython/html/static/style/style.min.css
@@ -1356,7 +1356,7 @@ div.input{page-break-inside:avoid;display:-webkit-box;-webkit-box-orient:horizon
 div.input_prompt{color:#000080;border-top:1px solid transparent}
 .CodeMirror{line-height:1.231em;height:auto;background:none;}
 .CodeMirror-scroll{overflow-y:hidden;overflow-x:auto}
-@-moz-document {.CodeMirror-scroll{overflow-x:hidden}}.CodeMirror-lines{padding:.4em}
+@-moz-document url-prefix(){.CodeMirror-scroll{overflow-x:hidden}}.CodeMirror-lines{padding:.4em}
 .CodeMirror-linenumber{padding:0 8px 0 4px}
 .CodeMirror-gutters{border-bottom-left-radius:4px;border-top-left-radius:4px}
 .CodeMirror pre{padding:0;border:0;border-radius:0;-webkit-border-radius:0;-moz-border-radius:0;border-radius:0}