diff --git a/intl/unicharutil/tests/NormalizationTest.cpp b/intl/unicharutil/tests/NormalizationTest.cpp
index 1b955a2ee43..8f6980932f9 100644
--- a/intl/unicharutil/tests/NormalizationTest.cpp
+++ b/intl/unicharutil/tests/NormalizationTest.cpp
@@ -10,6 +10,7 @@
 #include "nsString.h"
 #include "nsCharTraits.h"
 #include "nsServiceManagerUtils.h"
+#include "mozilla/Snprintf.h"
 
 struct testcaseLine {
   wchar_t* c1;
@@ -136,7 +137,6 @@ bool TestUnspecifiedCodepoint(uint32_t codepoint)
   bool rv = true;
   char16_t unicharArray[3];
   nsAutoString X, normalized;
-  char description[9];
 
   if (IS_IN_BMP(codepoint)) {
     unicharArray[0] = codepoint;
@@ -157,8 +157,11 @@ bool TestUnspecifiedCodepoint(uint32_t codepoint)
 
       X == NFC(X) == NFD(X) == NFKC(X) == NFKD(X)
   */
+  static const size_t len = 9;
+  char description[len];
+
   DEBUG_TESTCASE(X);
-  sprintf(description, "U+%04X", codepoint);
+  snprintf(description, len, "U+%04X", codepoint);
   NORMALIZE_AND_COMPARE(X, X, NFC, description);
   NORMALIZE_AND_COMPARE(X, X, NFD, description);
   NORMALIZE_AND_COMPARE(X, X, NFKC, description);
diff --git a/intl/unicharutil/tests/moz.build b/intl/unicharutil/tests/moz.build
index fce190db882..b9282c2fae9 100755
--- a/intl/unicharutil/tests/moz.build
+++ b/intl/unicharutil/tests/moz.build
@@ -8,7 +8,4 @@ SOURCES += [
     'NormalizationTest.cpp',
 ]
 
-# XXX: We should fix these warnings.
-ALLOW_COMPILER_WARNINGS = True
-
 FINAL_LIBRARY = 'xul-gtest'
diff --git a/intl/unicharutil/util/moz.build b/intl/unicharutil/util/moz.build
index 4aaa6eb33f4..ce2f3f0f5d7 100644
--- a/intl/unicharutil/util/moz.build
+++ b/intl/unicharutil/util/moz.build
@@ -43,7 +43,4 @@ if CONFIG['ENABLE_INTL_API']:
     CXXFLAGS += CONFIG['MOZ_ICU_CFLAGS']
     USE_LIBS += ['icu']
 
-if not CONFIG['GNU_CXX']:
-    ALLOW_COMPILER_WARNINGS = True
-
 DIST_INSTALL = True