diff --git a/intl/unicharutil/util/nsUnicodeProperties.cpp b/intl/unicharutil/util/nsUnicodeProperties.cpp
index 9d1a940968..e78725b036 100644
--- a/intl/unicharutil/util/nsUnicodeProperties.cpp
+++ b/intl/unicharutil/util/nsUnicodeProperties.cpp
@@ -158,16 +158,6 @@ IsClusterExtender(uint32_t aCh, uint8_t aCategory)
             (aCh >= 0xe0020 && aCh <= 0xe007f)); // emoji (flag) tag characters
 }
 
-bool IsClusterExtenderExcludingJoiners(uint32_t aCh, uint8_t aCategory)
-{
-    return ((aCategory >= HB_UNICODE_GENERAL_CATEGORY_SPACING_MARK &&
-             aCategory <= HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK) ||
-            (aCh >= 0xff9e && aCh <= 0xff9f) || // katakana sound marks
-            (aCh >= 0x1F3FB && aCh <= 0x1F3FF) || // fitzpatrick skin tone modifiers
-            (aCh >= 0xe0020 && aCh <= 0xe007f)); // emoji (flag) tag characters
-}
-
-
 enum HSType {
     HST_NONE = U_HST_NOT_APPLICABLE,
     HST_L    = U_HST_LEADING_JAMO,
diff --git a/intl/unicharutil/util/nsUnicodeProperties.h b/intl/unicharutil/util/nsUnicodeProperties.h
index 3a85a2ecb6..eaa066b7f6 100644
--- a/intl/unicharutil/util/nsUnicodeProperties.h
+++ b/intl/unicharutil/util/nsUnicodeProperties.h
@@ -216,12 +216,6 @@ inline bool IsClusterExtender(uint32_t aCh) {
   return IsClusterExtender(aCh, GetGeneralCategory(aCh));
 }
 
-bool IsClusterExtenderExcludingJoiners(uint32_t aCh, uint8_t aCategory);
-
-inline bool IsClusterExtenderExcludingJoiners(uint32_t aCh) {
-  return IsClusterExtenderExcludingJoiners(aCh, GetGeneralCategory(aCh));
-}
-
 // A simple iterator for a string of char16_t codepoints that advances
 // by Unicode grapheme clusters
 class ClusterIterator
diff --git a/layout/generic/nsTextFrameUtils.h b/layout/generic/nsTextFrameUtils.h
index c721799d03..6274705bc3 100644
--- a/layout/generic/nsTextFrameUtils.h
+++ b/layout/generic/nsTextFrameUtils.h
@@ -81,7 +81,7 @@ public:
   static bool
   IsSpaceCombiningSequenceTail(const char16_t* aChars, int32_t aLength) {
     return aLength > 0 &&
-      (mozilla::unicode::IsClusterExtenderExcludingJoiners(aChars[0]) ||
+      (mozilla::unicode::IsClusterExtender(aChars[0]) ||
        (IsBidiControl(aChars[0]) &&
         IsSpaceCombiningSequenceTail(aChars + 1, aLength - 1)
        )