diff --git a/mozilla/intl/uconv/ucvja/nsUnicodeToISO2022JP.cpp b/mozilla/intl/uconv/ucvja/nsUnicodeToISO2022JP.cpp
index d988b707f9a..05a89cfc2d3 100644
--- a/mozilla/intl/uconv/ucvja/nsUnicodeToISO2022JP.cpp
+++ b/mozilla/intl/uconv/ucvja/nsUnicodeToISO2022JP.cpp
@@ -173,7 +173,10 @@ NS_IMETHODIMP nsUnicodeToISO2022JP::ConvertNoBuffNoErr(
       if (res != NS_ERROR_UENC_NOMAPPING) break;
     }
 
-    if (i>=4) res = NS_ERROR_UENC_NOMAPPING;
+    if (i>=4) {
+      res = NS_ERROR_UENC_NOMAPPING;
+      src++;
+    }
     if (res != NS_OK) break;
 
     bcw = destEnd - dest;