--- a/dom/base/nsTextFragment.cpp
+++ b/dom/base/nsTextFragment.cpp
@@ -456,15 +456,15 @@ nsTextFragment::UpdateBidiFlag(const cha
       char16_t ch1 = *cp++;
       uint32_t utf32Char = ch1;
       if (NS_IS_HIGH_SURROGATE(ch1) &&
           cp < end &&
           NS_IS_LOW_SURROGATE(*cp)) {
         char16_t ch2 = *cp++;
         utf32Char = SURROGATE_TO_UCS4(ch1, ch2);
       }
-      if (UTF32_CHAR_IS_BIDI(utf32Char) || IsBidiControl(utf32Char)) {
+      if (UTF32_CHAR_IS_BIDI(utf32Char) || IsBidiControlRTL(utf32Char)) {
         mState.mIsBidi = true;
         break;
       }
     }
   }
 }

--- a/intl/unicharutil/util/nsBidiUtils.h
+++ b/intl/unicharutil/util/nsBidiUtils.h
@@ -106,29 +106,52 @@ typedef enum nsCharType nsCharType;
 
   /**
    * Give a UTF-32 codepoint
    * return true if the codepoint is a Bidi control character (LRM, RLM, ALM;
    * LRE, RLE, PDF, LRO, RLO; LRI, RLI, FSI, PDI).
    * Return false, otherwise
    */
 #define LRM_CHAR 0x200e
+#define RLM_CHAR 0x200f
+
 #define LRE_CHAR 0x202a
+#define RLE_CHAR 0x202b
+#define PDF_CHAR 0x202c
+#define LRO_CHAR 0x202d
 #define RLO_CHAR 0x202e
+
 #define LRI_CHAR 0x2066
+#define RLI_CHAR 0x2067
+#define FSI_CHAR 0x2068
 #define PDI_CHAR 0x2069
+
 #define ALM_CHAR 0x061C
    inline bool IsBidiControl(uint32_t aChar) {
      return ((LRE_CHAR <= aChar && aChar <= RLO_CHAR) ||
              (LRI_CHAR <= aChar && aChar <= PDI_CHAR) ||
              (aChar == ALM_CHAR) ||
              (aChar & 0xfffffe) == LRM_CHAR);
    }
 
   /**
+   * Give a UTF-32 codepoint
+   * Return true if the codepoint is a Bidi control character that may result
+   * in RTL directionality and therefore needs to trigger bidi resolution;
+   * return false otherwise.
+   */
+   inline bool IsBidiControlRTL(uint32_t aChar) {
+     return aChar == RLM_CHAR ||
+            aChar == RLE_CHAR ||
+            aChar == RLO_CHAR ||
+            aChar == RLI_CHAR ||
+            aChar == ALM_CHAR;
+   }
+
+  /**
    * Give an nsString.
    * @return true if the string contains right-to-left characters
    */
    bool HasRTLChars(const nsAString& aString);
 
 // These values are shared with Preferences dialog
 //  ------------------
 //  If Pref values are to be changed