diff --git a/src/librustdoc/html/static/themes/ayu.css b/src/librustdoc/html/static/themes/ayu.css
index fd8153519afaf..7374aee71f8f8 100644
--- a/src/librustdoc/html/static/themes/ayu.css
+++ b/src/librustdoc/html/static/themes/ayu.css
@@ -266,7 +266,7 @@ a {
 
 .stab.portability > code {
 	color: #e6e1cf;
-	background-color: transparent;
+	background: none;
 }
 
 #help > div {
diff --git a/src/librustdoc/html/static/themes/dark.css b/src/librustdoc/html/static/themes/dark.css
index 9eeccd038a2ff..88ac3252bb4b2 100644
--- a/src/librustdoc/html/static/themes/dark.css
+++ b/src/librustdoc/html/static/themes/dark.css
@@ -222,10 +222,7 @@ a.test-arrow {
 .stab.unstable { background: #FFF5D6; border-color: #FFC600; color: #2f2f2f; }
 .stab.deprecated { background: #F3DFFF; border-color: #7F0087; color: #2f2f2f; }
 .stab.portability { background: #C4ECFF; border-color: #7BA5DB; color: #2f2f2f; }
-
-.stab.portability > code {
-	color: #ddd;
-}
+.stab.portability > code { background: none; }
 
 #help > div {
 	background: #4d4d4d;
diff --git a/src/librustdoc/html/static/themes/light.css b/src/librustdoc/html/static/themes/light.css
index 814043b35ae61..9bc21102aaae6 100644
--- a/src/librustdoc/html/static/themes/light.css
+++ b/src/librustdoc/html/static/themes/light.css
@@ -220,10 +220,7 @@ a.test-arrow {
 .stab.unstable { background: #FFF5D6; border-color: #FFC600; }
 .stab.deprecated { background: #F3DFFF; border-color: #7F0087; }
 .stab.portability { background: #C4ECFF; border-color: #7BA5DB; }
-
-.stab.portability > code {
-	color: #000;
-}
+.stab.portability > code { background: none; }
 
 #help > div {
 	background: #e9e9e9;