diff --git a/lib/themeroller.js b/lib/themeroller.js
index a475e3eb..b4337381 100644
--- a/lib/themeroller.js
+++ b/lib/themeroller.js
@@ -128,9 +128,19 @@ function ThemeRoller( options ) {
 	// TODO: Remove `filter` style when dropping support for IE8 and earlier.
 	vars.opacityOverlayPerc = vars.opacityOverlay;
 	vars.opacityShadowPerc = vars.opacityShadow;
-	if ( semver.gte( this.jqueryUi.pkg.version, "1.10.0" ) ) {
+	if ( semver.lt( this.jqueryUi.pkg.version, "1.10.0" ) ) {
 
-		// For version >= 1.10.0, filter has its own separate line and variable name.
+		// For version <1.10.0, `opacity` (W3C) and `filter` (IE) are combined
+		// into the same line.
+		opacityFix = function( opacity ) {
+			return /* w3c */ ( opacity / 100 ).toString().replace( /^0\./, "." ) + /* IE */ ";filter:Alpha(Opacity=" + opacity + ")";
+		};
+		vars.opacityOverlay = opacityFix( vars.opacityOverlay );
+		vars.opacityShadow = opacityFix( vars.opacityShadow );
+	} else if ( semver.lt( this.jqueryUi.pkg.version, "1.13.0" ) ) {
+
+		// For version >=1.10.0 <1.13.0, `filter` has its own separate line
+		// and variable name.
 		opacityFix = function( opacity ) {
 			return ( opacity / 100 ).toString().replace( /^0\./, "." );
 		};
@@ -143,10 +153,16 @@ function ThemeRoller( options ) {
 		vars.opacityShadow = opacityFix( vars.opacityShadow );
 	} else {
 
-		// For version < 1.10.0, opacity (w3c) and filter (IE) are combined into the same line.
+		// For version >=1.13.0, `-ms-filter` has its own separate line
+		// and variable name.
 		opacityFix = function( opacity ) {
-			return /* w3c */ ( opacity / 100 ).toString().replace( /^0\./, "." ) + /* IE */ ";filter:Alpha(Opacity=" + opacity + ")";
+			return ( opacity / 100 ).toString().replace( /^0\./, "." );
+		};
+		opacityFilter = function( opacity ) {
+			return "\"alpha(opacity=" + opacity + ")\"";
 		};
+		vars.opacityFilterOverlay = opacityFilter( vars.opacityOverlay );
+		vars.opacityFilterShadow = opacityFilter( vars.opacityShadow );
 		vars.opacityOverlay = opacityFix( vars.opacityOverlay );
 		vars.opacityShadow = opacityFix( vars.opacityShadow );
 	}
@@ -210,7 +226,7 @@ function ThemeRoller( options ) {
 	if ( !this.name ) {
 
 		// Pick name based on theme gallery vs. our vars
-		themeGallery = require( "./themeroller-themegallery" )();
+		themeGallery = require( "./themeroller-themegallery" )( this.jqueryUi );
 		themeGallery.some( function( theme ) {
 			found = theme.isEqual( self );
 			if ( found ) {
diff --git a/test/fixtures/jquery-ui-1.13.2/themes/smoothness.css b/test/fixtures/jquery-ui-1.13.2/themes/smoothness.css
index e4fa82c1..8388761c 100644
--- a/test/fixtures/jquery-ui-1.13.2/themes/smoothness.css
+++ b/test/fixtures/jquery-ui-1.13.2/themes/smoothness.css
@@ -438,7 +438,7 @@ a.ui-button:active,
 .ui-widget-overlay {
 	background: #aaaaaa;
 	opacity: .3;
-	-ms-filter: Alpha(Opacity=30); /* support: IE8 */
+	-ms-filter: "alpha(opacity=30)"; /* support: IE8 */
 }
 .ui-widget-shadow {
 	-webkit-box-shadow: -8px -8px 8px #aaaaaa;