diff --git a/build/autoconf/icu.m4 b/build/autoconf/icu.m4
index a03132fd93b..e0eb6234697 100644
--- a/build/autoconf/icu.m4
+++ b/build/autoconf/icu.m4
@@ -142,6 +142,7 @@ if test -z "$BUILDING_JS" -o -n "$JS_STANDALONE"; then
         ICU_CPPFLAGS="$ICU_CPPFLAGS -DUCONFIG_NO_TRANSLITERATION"
         ICU_CPPFLAGS="$ICU_CPPFLAGS -DUCONFIG_NO_REGULAR_EXPRESSIONS"
         ICU_CPPFLAGS="$ICU_CPPFLAGS -DUCONFIG_NO_BREAK_ITERATION"
+        ICU_CPPFLAGS="$ICU_CPPFLAGS -DUCONFIG_NO_IDNA"
         # we don't need to pass data to and from legacy char* APIs
         ICU_CPPFLAGS="$ICU_CPPFLAGS -DU_CHARSET_IS_UTF8"
         # make sure to not accidentally pick up system-icu headers
diff --git a/netwerk/dns/moz.build b/netwerk/dns/moz.build
index d1d259e1218..7b49d6caa1a 100644
--- a/netwerk/dns/moz.build
+++ b/netwerk/dns/moz.build
@@ -40,6 +40,7 @@ UNIFIED_SOURCES += [
     'DNSRequestChild.cpp',
     'DNSRequestParent.cpp',
     'GetAddrInfo.cpp',
+    'nameprep.c',
     'nsDNSService2.cpp',
     'nsIDNService.cpp',
     'punycode.c',
@@ -68,13 +69,3 @@ LOCAL_INCLUDES += [
 
 if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'gonk' and CONFIG['ANDROID_VERSION'] > '19':
     CXXFLAGS += ['-I%s/bionic/libc/dns/include' % CONFIG['ANDROID_SOURCE']]
-
-if CONFIG['ENABLE_INTL_API']:
-    DEFINES['IDNA2008'] = True
-    CXXFLAGS += CONFIG['MOZ_ICU_CFLAGS']
-    CFLAGS += CONFIG['MOZ_ICU_CFLAGS']
-    USE_LIBS += ['icu']
-else:
-    UNIFIED_SOURCES += [
-        'nameprep.c',
-    ]
diff --git a/netwerk/dns/nsIDNService.cpp b/netwerk/dns/nsIDNService.cpp
index e2c1b8a2ca7..28a6db24867 100644
--- a/netwerk/dns/nsIDNService.cpp
+++ b/netwerk/dns/nsIDNService.cpp
@@ -17,16 +17,6 @@
 #include "nsISupportsPrimitives.h"
 #include "punycode.h"
 
-#ifdef IDNA2008
-// Currently we use the transitional processing option -- see
-// http://unicode.org/reports/tr46/
-// To switch to non-transitional processing, change the value of this flag
-// and kTransitionalProcessing in netwerk/test/unit/test_idna2008.js to false
-// (patch in bug 1218179).
-const bool kIDNA2008_TransitionalProcessing = true;
-
-#include "ICUUtils.h"
-#endif
 
 using namespace mozilla::unicode;
 
@@ -133,91 +123,18 @@ void nsIDNService::prefsChanged(nsIPrefBranch *prefBranch, const char16_t *pref)
 
 nsIDNService::nsIDNService()
 {
-#ifdef IDNA2008
-  uint32_t IDNAOptions = UIDNA_CHECK_BIDI | UIDNA_CHECK_CONTEXTJ;
-  if (!kIDNA2008_TransitionalProcessing) {
-    IDNAOptions |= UIDNA_NONTRANSITIONAL_TO_UNICODE;
-  }
-  UErrorCode errorCode = U_ZERO_ERROR;
-  mIDNA = uidna_openUTS46(IDNAOptions, &errorCode);
-#else
   if (idn_success != idn_nameprep_create(nullptr, &mNamePrepHandle))
     mNamePrepHandle = nullptr;
 
   mNormalizer = do_GetService(NS_UNICODE_NORMALIZER_CONTRACTID);
   /* member initializers and constructor code */
-#endif
 }
 
 nsIDNService::~nsIDNService()
 {
-#ifdef IDNA2008
-  uidna_close(mIDNA);
-#else
   idn_nameprep_destroy(mNamePrepHandle);
-#endif
 }
 
-#ifdef IDNA2008
-nsresult
-nsIDNService::IDNA2008ToUnicode(const nsACString& input, nsAString& output)
-{
-  NS_ConvertUTF8toUTF16 inputStr(input);
-  UIDNAInfo info = UIDNA_INFO_INITIALIZER;
-  UErrorCode errorCode = U_ZERO_ERROR;
-  int32_t inLen = inputStr.Length();
-  int32_t outMaxLen = inLen - kACEPrefixLen + 1;
-  UChar outputBuffer[kMaxDNSNodeLen + 1];
-
-  int32_t outLen = uidna_labelToUnicode(mIDNA, (const UChar*)inputStr.get(),
-                                        inLen, outputBuffer, outMaxLen,
-                                        &info, &errorCode);
-  if (info.errors != 0) {
-    return NS_ERROR_FAILURE;
-  }
-
-  if (U_SUCCESS(errorCode)) {
-    ICUUtils::AssignUCharArrayToString(outputBuffer, outLen, output);
-  }
-
-  return ICUUtils::UErrorToNsResult(errorCode);
-}
-
-nsresult
-nsIDNService::IDNA2008StringPrep(const nsAString& input,
-                                 nsAString& output,
-                                 stringPrepFlag flag)
-{
-  UIDNAInfo info = UIDNA_INFO_INITIALIZER;
-  UErrorCode errorCode = U_ZERO_ERROR;
-  int32_t inLen = input.Length();
-  int32_t outMaxLen = kMaxDNSNodeLen + 1;
-  UChar outputBuffer[kMaxDNSNodeLen + 1];
-
-  int32_t outLen =
-    uidna_labelToUnicode(mIDNA, (const UChar*)PromiseFlatString(input).get(),
-                         inLen, outputBuffer, outMaxLen, &info, &errorCode);
-  nsresult rv = ICUUtils::UErrorToNsResult(errorCode);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  // Output the result of nameToUnicode even if there were errors
-  ICUUtils::AssignUCharArrayToString(outputBuffer, outLen, output);
-
-  if (flag == eStringPrepIgnoreErrors) {
-    return NS_OK;
-  }
-
-  if (info.errors != 0) {
-    if (flag == eStringPrepForDNS) {
-      output.Truncate();
-    }
-    rv = NS_ERROR_FAILURE;
-  }
-
-  return rv;
-}
-#endif
-
 NS_IMETHODIMP nsIDNService::ConvertUTF8toACE(const nsACString & input, nsACString & ace)
 {
   return UTF8toACE(input, ace, eStringPrepForDNS);
@@ -479,7 +396,6 @@ static nsresult utf16ToUcs4(const nsAString& in,
   return NS_OK;
 }
 
-#ifndef IDNA2008
 static void ucs4toUtf16(const uint32_t *in, nsAString& out)
 {
   while (*in) {
@@ -492,7 +408,6 @@ static void ucs4toUtf16(const uint32_t *in, nsAString& out)
     in++;
   }
 }
-#endif
 
 static nsresult punycode(const nsAString& in, nsACString& out)
 {
@@ -547,9 +462,6 @@ static nsresult punycode(const nsAString& in, nsACString& out)
 nsresult nsIDNService::stringPrep(const nsAString& in, nsAString& out,
                                   stringPrepFlag flag)
 {
-#ifdef IDNA2008
-  return IDNA2008StringPrep(in, out, flag);
-#else
   if (!mNamePrepHandle || !mNormalizer)
     return NS_ERROR_FAILURE;
 
@@ -611,7 +523,6 @@ nsresult nsIDNService::stringPrep(const nsAString& in, nsAString& out,
   }
 
   return rv;
-#endif
 }
 
 nsresult nsIDNService::stringPrepAndACE(const nsAString& in, nsACString& out,
@@ -701,11 +612,6 @@ nsresult nsIDNService::decodeACE(const nsACString& in, nsACString& out,
     return NS_OK;
   }
 
-  nsAutoString utf16;
-#ifdef IDNA2008
-  nsresult result = IDNA2008ToUnicode(in, utf16);
-  NS_ENSURE_SUCCESS(result, result);
-#else
   // RFC 3490 - 4.2 ToUnicode
   // The ToUnicode output never contains more code points than its input.
   punycode_uint output_length = in.Length() - kACEPrefixLen + 1;
@@ -724,9 +630,9 @@ nsresult nsIDNService::decodeACE(const nsACString& in, nsACString& out,
 
   // UCS4 -> UTF8
   output[output_length] = 0;
+  nsAutoString utf16;
   ucs4toUtf16(output, utf16);
   delete [] output;
-#endif
   if (flag != eStringPrepForUI || isLabelSafe(utf16)) {
     CopyUTF16toUTF8(utf16, out);
   } else {
diff --git a/netwerk/dns/nsIDNService.h b/netwerk/dns/nsIDNService.h
index b0fa5101e89..c97b9d67b61 100644
--- a/netwerk/dns/nsIDNService.h
+++ b/netwerk/dns/nsIDNService.h
@@ -10,14 +10,8 @@
 #include "nsCOMPtr.h"
 #include "nsIObserver.h"
 #include "nsWeakReference.h"
-
-#ifdef IDNA2008
-#include "unicode/uidna.h"
-#else
 #include "nsIUnicodeNormalizer.h"
 #include "nsIDNKitInterface.h"
-#endif
-
 #include "nsString.h"
 
 class nsIPrefBranch;
@@ -149,23 +143,8 @@ private:
    */
   bool illegalScriptCombo(int32_t script, int32_t& savedScript);
 
-#ifdef IDNA2008
-  /**
-   * Convert a DNS label from ASCII to Unicode using IDNA2008
-   */
-  nsresult IDNA2008ToUnicode(const nsACString& input, nsAString& output);
-
-  /**
-   * Convert a DNS label to a normalized form conforming to IDNA2008
-   */
-  nsresult IDNA2008StringPrep(const nsAString& input, nsAString& output,
-                              stringPrepFlag flag);
-
-  UIDNA* mIDNA;
-#else
   idn_nameprep_t mNamePrepHandle;
   nsCOMPtr<nsIUnicodeNormalizer> mNormalizer;
-#endif
   nsXPIDLString mIDNBlacklist;
 
   /**
diff --git a/netwerk/standalone/moz.build b/netwerk/standalone/moz.build
index 60a16aa2678..dcc13e07c30 100644
--- a/netwerk/standalone/moz.build
+++ b/netwerk/standalone/moz.build
@@ -43,7 +43,6 @@ LOCAL_INCLUDES = [
     '../dns',
 ]
 
-DEFINES['IDNA2008'] = False
 DEFINES['MOZILLA_INTERNAL_API'] = True
 DEFINES['MOZILLA_XPCOMRT_API'] = True
 DEFINES['MOZILLA_EXTERNAL_LINKAGE'] = True