diff --git a/content/xslt/src/base/txError.h b/content/xslt/src/base/txError.h
index 94933bd550bc..fa33d21d3f20 100644
--- a/content/xslt/src/base/txError.h
+++ b/content/xslt/src/base/txError.h
@@ -141,4 +141,7 @@
 #define NS_ERROR_XSLT_BAD_NODE_NAME                    \
     NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_XSLT, 30)
 
+#define NS_ERROR_XSLT_VAR_ALREADY_SET                  \
+    NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_XSLT, 31)
+
 #endif // __TX_ERROR
diff --git a/content/xslt/src/xslt/txVariableMap.h b/content/xslt/src/xslt/txVariableMap.h
index 03aae275f5a7..e99d7646b2bd 100644
--- a/content/xslt/src/xslt/txVariableMap.h
+++ b/content/xslt/src/xslt/txVariableMap.h
@@ -77,6 +77,9 @@ txVariableMap::bindVariable(const txExpandedName& aName, txAExprResult* aValue)
     if (NS_SUCCEEDED(rv)) {
         NS_ADDREF(aValue);
     }
+    else if (rv == NS_ERROR_XSLT_ALREADY_SET) {
+        rv = NS_ERROR_XSLT_VAR_ALREADY_SET;
+    }
     return rv;
 }
 
diff --git a/dom/locales/en-US/chrome/xslt/xslt.properties b/dom/locales/en-US/chrome/xslt/xslt.properties
index 45fe06a25ebf..e40899ca1419 100644
--- a/dom/locales/en-US/chrome/xslt/xslt.properties
+++ b/dom/locales/en-US/chrome/xslt/xslt.properties
@@ -37,6 +37,7 @@
 
 1  = Parsing an XSLT stylesheet failed.
 2  = Parsing an XPath expression failed.
+3  = 
 4  = XSLT transformation failed.
 5  = Invalid XSLT/XPath function.
 6  = XSLT Stylesheet (possibly) contains a recursion.
@@ -61,6 +62,10 @@
 25 = XPath parse failure: illegal character found:
 26 = XPath parse failure: binary operator expected:
 27 = An XSLT stylesheet load was blocked for security reasons.
+28 = Evaluating an invalid expression.
+29 = Unbalanced curly brace.
+30 = Creating an element with an invalid QName.
+31 = Variable binding shadows variable binding within the same template.
 
 LoadingError = Error loading stylesheet: %S
 TransformError = Error during XSLT transformation: %S