--- a/intl/uconv/nsTextToSubURI.cpp
+++ b/intl/uconv/nsTextToSubURI.cpp
@@ -124,16 +124,17 @@ NS_IMETHODIMP  nsTextToSubURI::UnEscapeA
   if (nullptr == unescaped)
     return NS_ERROR_OUT_OF_MEMORY;
   unescaped = nsUnescape(unescaped);
   NS_ASSERTION(unescaped, "nsUnescape returned null");
 
   nsDependentCString label(charset);
   nsAutoCString encoding;
   if (!EncodingUtils::FindEncodingForLabelNoReplacement(label, encoding)) {
+    free(unescaped);
     return NS_ERROR_UCONV_NOCONV;
   }
   nsCOMPtr<nsIUnicodeDecoder> decoder =
     EncodingUtils::DecoderForEncoding(encoding);
   char16_t *pBuf = nullptr;
   int32_t len = strlen(unescaped);
   int32_t outlen = 0;
   if (NS_SUCCEEDED(rv = decoder->GetMaxLength(unescaped, len, &outlen))) {