--- a/xpcom/string/nsUTF8Utils.h
+++ b/xpcom/string/nsUTF8Utils.h
@@ -12,16 +12,22 @@
 
 #include "nscore.h"
 #include "mozilla/Assertions.h"
 #include "mozilla/SSE.h"
 #include "mozilla/TypeTraits.h"
 
 #include "nsCharTraits.h"
 
+#ifdef MOZILLA_INTERNAL_API
+#define UTF8UTILS_WARNING(msg) NS_WARNING(msg)
+#else
+#define UTF8UTILS_WARNING(msg)
+#endif
+
 class UTF8traits
 {
 public:
   static bool isASCII(char aChar)
   {
     return (aChar & 0x80) == 0x00;
   }
   static bool isInSeq(char aChar)
@@ -205,17 +211,17 @@ public:
       *aBuffer = p;
       return c;
     } else if (NS_IS_HIGH_SURROGATE(c)) { // U+D800 - U+DBFF
       if (p == aEnd) {
         // Found a high surrogate at the end of the buffer. Flag this
         // as an error and return the Unicode replacement
         // character 0xFFFD.
 
-        NS_WARNING("Unexpected end of buffer after high surrogate");
+        UTF8UTILS_WARNING("Unexpected end of buffer after high surrogate");
 
         if (aErr) {
           *aErr = true;
         }
         *aBuffer = p;
         return 0xFFFD;
       }
 
@@ -238,32 +244,32 @@ public:
         // a low surrogate. Flag this as an error and return the
         // Unicode replacement character 0xFFFD.  Note that the
         // pointer to the next character points to the second 16-bit
         // value, not beyond it, as per Unicode 5.0.0 Chapter 3 C10,
         // only the first code unit of an illegal sequence must be
         // treated as an illegally terminated code unit sequence
         // (also Chapter 3 D91, "isolated [not paired and ill-formed]
         // UTF-16 code units in the range D800..DFFF are ill-formed").
-        NS_WARNING("got a High Surrogate but no low surrogate");
+        UTF8UTILS_WARNING("got a High Surrogate but no low surrogate");
 
         if (aErr) {
           *aErr = true;
         }
         *aBuffer = p - 1;
         return 0xFFFD;
       }
     } else { // U+DC00 - U+DFFF
       // DC00- DFFF - Low Surrogate
 
       // Found a low surrogate w/o a preceding high surrogate. Flag
       // this as an error and return the Unicode replacement
       // character 0xFFFD.
 
-      NS_WARNING("got a low Surrogate but no high surrogate");
+      UTF8UTILS_WARNING("got a low Surrogate but no high surrogate");
       if (aErr) {
         *aErr = true;
       }
       *aBuffer = p;
       return 0xFFFD;
     }
 
     MOZ_ASSERT_UNREACHABLE("Impossible UCS-2 character value.");
@@ -487,17 +493,17 @@ public:
         if (p == end) {
           // Treat broken characters as the Unicode
           // replacement character 0xFFFD (0xEFBFBD in
           // UTF-8)
           *out++ = '\xEF';
           *out++ = '\xBF';
           *out++ = '\xBD';
 
-          NS_WARNING("String ending in half a surrogate pair!");
+          UTF8UTILS_WARNING("String ending in half a surrogate pair!");
 
           break;
         }
         c = *p;
 
         if (NS_IS_LOW_SURROGATE(c)) {
           // DC00- DFFF - Low Surrogate
           // N = (H - D800) *400 + 10000 + ( L - DC00 )
@@ -520,27 +526,27 @@ public:
           // 16-bit value, not beyond it, as per Unicode 5.0.0
           // Chapter 3 C10, only the first code unit of an illegal
           // sequence must be treated as an illegally terminated
           // code unit sequence (also Chapter 3 D91, "isolated [not
           // paired and ill-formed] UTF-16 code units in the range
           // D800..DFFF are ill-formed").
           p--;
 
-          NS_WARNING("got a High Surrogate but no low surrogate");
+          UTF8UTILS_WARNING("got a High Surrogate but no low surrogate");
         }
       } else { // U+DC00 - U+DFFF
         // Treat broken characters as the Unicode replacement
         // character 0xFFFD (0xEFBFBD in UTF-8)
         *out++ = '\xEF';
         *out++ = '\xBF';
         *out++ = '\xBD';
 
         // DC00- DFFF - Low Surrogate
-        NS_WARNING("got a low Surrogate but no high surrogate");
+        UTF8UTILS_WARNING("got a low Surrogate but no high surrogate");
       }
     }
 
     mBuffer = out;
   }
 
   void write_terminator()
   {
@@ -586,17 +592,17 @@ public:
       } else if (0xD800 == (0xFC00 & c)) { // U+D800 - U+DBFF
         ++p;
         if (p == end) {
           // Treat broken characters as the Unicode
           // replacement character 0xFFFD (0xEFBFBD in
           // UTF-8)
           mSize += 3;
 
-          NS_WARNING("String ending in half a surrogate pair!");
+          UTF8UTILS_WARNING("String ending in half a surrogate pair!");
 
           break;
         }
         c = *p;
 
         if (0xDC00 == (0xFC00 & c)) {
           mSize += 4;
         } else {
@@ -609,24 +615,24 @@ public:
           // the one beyond it, as per Unicode 5.0.0 Chapter 3 C10,
           // only the first code unit of an illegal sequence must
           // be treated as an illegally terminated code unit
           // sequence (also Chapter 3 D91, "isolated [not paired and
           // ill-formed] UTF-16 code units in the range D800..DFFF
           // are ill-formed").
           p--;
 
-          NS_WARNING("got a high Surrogate but no low surrogate");
+          UTF8UTILS_WARNING("got a high Surrogate but no low surrogate");
         }
       } else { // U+DC00 - U+DFFF
         // Treat broken characters as the Unicode replacement
         // character 0xFFFD (0xEFBFBD in UTF-8)
         mSize += 3;
 
-        NS_WARNING("got a low Surrogate but no high surrogate");
+        UTF8UTILS_WARNING("got a low Surrogate but no high surrogate");
       }
     }
   }
 
 private:
   size_t mSize;
 };
 
@@ -734,9 +740,11 @@ RewindToPriorUTF8Codepoint(const Char* u
                 "UTF-8 data must be in 8-bit units");
   static_assert(mozilla::IsUnsigned<UnsignedT>::value, "index type must be unsigned");
   while (index > 0 && (utf8Chars[index] & 0xC0) == 0x80)
     --index;
 
   return index;
 }
 
+#undef UTF8UTILS_WARNING
+
 #endif /* !defined(nsUTF8Utils_h_) */