diff --git a/content/html/document/src/nsHTMLDocument.cpp b/content/html/document/src/nsHTMLDocument.cpp
index 462f312e7226..a390447c5b60 100644
--- a/content/html/document/src/nsHTMLDocument.cpp
+++ b/content/html/document/src/nsHTMLDocument.cpp
@@ -2796,6 +2796,7 @@ static PRBool IsInline(eHTMLTags aTag)
     case  eHTMLTag_td:
     case  eHTMLTag_textarea:
     case  eHTMLTag_tt:
+    case  eHTMLTag_u:
     case  eHTMLTag_var:
     case  eHTMLTag_wbr:
            
diff --git a/layout/html/document/src/nsHTMLDocument.cpp b/layout/html/document/src/nsHTMLDocument.cpp
index 462f312e7226..a390447c5b60 100644
--- a/layout/html/document/src/nsHTMLDocument.cpp
+++ b/layout/html/document/src/nsHTMLDocument.cpp
@@ -2796,6 +2796,7 @@ static PRBool IsInline(eHTMLTags aTag)
     case  eHTMLTag_td:
     case  eHTMLTag_textarea:
     case  eHTMLTag_tt:
+    case  eHTMLTag_u:
     case  eHTMLTag_var:
     case  eHTMLTag_wbr: