diff --git a/lib/themeroller.js b/lib/themeroller.js
index 4204da6..d67a8d8 100644
--- a/lib/themeroller.js
+++ b/lib/themeroller.js
@@ -112,17 +112,33 @@ function ThemeRoller( baseThemeCss, vars, options ) {
 
 	} else {
 
-		// For version >= 1.10.0, filter has its own separate line and variable name.
-		opacityFix = function( 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 );
+		if ( options.version && semver.lt( options.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\./, "." );
+			};
+			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 );
+		}
+		else {
+			// For version >= 1.13.0, filter has its own separate line and variable name.
+			opacityFix = function( 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 );
+		}
 	}
 
 	// Add '#' in the beginning of the colors if needed
diff --git a/test/fixtures/jquery-ui-1.12/base/theme.css b/test/fixtures/jquery-ui-1.12/base/theme.css
index c7ad484..da03b7e 100644
--- a/test/fixtures/jquery-ui-1.12/base/theme.css
+++ b/test/fixtures/jquery-ui-1.12/base/theme.css
@@ -139,18 +139,18 @@
 .ui-widget-content .ui-priority-secondary,
 .ui-widget-header .ui-priority-secondary {
 	opacity: .7;
-	filter:Alpha(Opacity=70); /* support: IE8 */
+	filter: "alpha(opacity=70)"; /* support: IE8 */
 	font-weight: normal;
 }
 .ui-state-disabled,
 .ui-widget-content .ui-state-disabled,
 .ui-widget-header .ui-state-disabled {
 	opacity: .35;
-	filter:Alpha(Opacity=35); /* support: IE8 */
+	filter: "alpha(opacity=35)"; /* support: IE8 */
 	background-image: none;
 }
 .ui-state-disabled .ui-icon {
-	filter:Alpha(Opacity=35); /* support: IE8 - See #6059 */
+	filter: "alpha(opacity=35)"; /* support: IE8 - See #6059 */
 }
 
 /* Icons
@@ -398,13 +398,13 @@
 .ui-widget-overlay {
 	background: #aaaaaa/*{bgColorOverlay}*/ url("images/ui-bg_flat_0_aaaaaa_40x100.png")/*{bgImgUrlOverlay}*/ 50%/*{bgOverlayXPos}*/ 50%/*{bgOverlayYPos}*/ repeat-x/*{bgOverlayRepeat}*/;
 	opacity: .3/*{opacityOverlay}*/;
-	filter: Alpha(Opacity=30)/*{opacityFilterOverlay}*/; /* support: IE8 */
+	filter: "alpha(opacity=30)"/*{opacityFilterOverlay}*/; /* support: IE8 */
 }
 .ui-widget-shadow {
 	margin: -8px/*{offsetTopShadow}*/ 0 0 -8px/*{offsetLeftShadow}*/;
 	padding: 8px/*{thicknessShadow}*/;
 	background: #aaaaaa/*{bgColorShadow}*/ url("images/ui-bg_flat_0_aaaaaa_40x100.png")/*{bgImgUrlShadow}*/ 50%/*{bgShadowXPos}*/ 50%/*{bgShadowYPos}*/ repeat-x/*{bgShadowRepeat}*/;
 	opacity: .3/*{opacityShadow}*/;
-	filter: Alpha(Opacity=30)/*{opacityFilterShadow}*/; /* support: IE8 */
+	filter: "alpha(opacity=30)"/*{opacityFilterShadow}*/; /* support: IE8 */
 	border-radius: 8px/*{cornerRadiusShadow}*/;
 }
diff --git a/test/fixtures/jquery-ui-1.12/themes/base.css b/test/fixtures/jquery-ui-1.12/themes/base.css
index e041db2..37f8ba0 100644
--- a/test/fixtures/jquery-ui-1.12/themes/base.css
+++ b/test/fixtures/jquery-ui-1.12/themes/base.css
@@ -139,18 +139,18 @@
 .ui-widget-content .ui-priority-secondary,
 .ui-widget-header .ui-priority-secondary {
 	opacity: .7;
-	filter:Alpha(Opacity=70); /* support: IE8 */
+	filter: "alpha(opacity=70)"; /* support: IE8 */
 	font-weight: normal;
 }
 .ui-state-disabled,
 .ui-widget-content .ui-state-disabled,
 .ui-widget-header .ui-state-disabled {
 	opacity: .35;
-	filter:Alpha(Opacity=35); /* support: IE8 */
+	filter: "alpha(opacity=35)"; /* support: IE8 */
 	background-image: none;
 }
 .ui-state-disabled .ui-icon {
-	filter:Alpha(Opacity=35); /* support: IE8 - See #6059 */
+	filter: "alpha(opacity=35)"; /* support: IE8 - See #6059 */
 }
 
 /* Icons
@@ -398,13 +398,13 @@
 .ui-widget-overlay {
 	background: #aaaaaa;
 	opacity: .3;
-	filter: Alpha(Opacity=30); /* support: IE8 */
+	filter: "alpha(opacity=30)"; /* support: IE8 */
 }
 .ui-widget-shadow {
 	margin: 0px 0 0 0px;
 	padding: 5px;
 	background: #666666;
 	opacity: .3;
-	filter: Alpha(Opacity=30); /* support: IE8 */
+	filter: "alpha(opacity=30)"; /* support: IE8 */
 	border-radius: 8px;
 }