diff --git a/build/autoconf/icu.m4 b/build/autoconf/icu.m4
index 5c606127211c..32fc84f30dd9 100644
--- a/build/autoconf/icu.m4
+++ b/build/autoconf/icu.m4
@@ -91,9 +91,16 @@ if test -n "$USE_ICU"; then
     AC_DEFINE(U_USING_ICU_NAMESPACE,0)
 
     if test -z "$MOZ_SYSTEM_ICU"; then
-        if test -z "$YASM" -a -z "$GNU_AS" -a "$COMPILE_ENVIRONMENT"; then
-            AC_MSG_ERROR([Building ICU requires either yasm or a GNU assembler. If you do not have either of those available for this platform you must use --without-intl-api])
-        fi
+        case "$OS_TARGET:$CPU_ARCH" in
+        WINNT:aarch64)
+            dnl we use non-yasm, non-GNU as solutions here.
+            ;;
+        *)
+            if test -z "$YASM" -a -z "$GNU_AS" -a "$COMPILE_ENVIRONMENT"; then
+                AC_MSG_ERROR([Building ICU requires either yasm or a GNU assembler. If you do not have either of those available for this platform you must use --without-intl-api])
+            fi
+            ;;
+        esac
         dnl We build ICU as a static library.
         AC_DEFINE(U_STATIC_IMPLEMENTATION)
     fi
diff --git a/config/external/icu/data/genicudata.py b/config/external/icu/data/genicudata.py
new file mode 100644
index 000000000000..043dc8cd42d5
--- /dev/null
+++ b/config/external/icu/data/genicudata.py
@@ -0,0 +1,14 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+def main(output, data_file, data_symbol):
+    output.write('''    AREA .rdata,ALIGN=4,DATA,READONLY
+    EXPORT _{data_symbol}[DATA]
+_{data_symbol}
+    INCBIN {data_file}
+    END
+'''.format(data_file=data_file, data_symbol=data_symbol))
diff --git a/config/external/icu/data/moz.build b/config/external/icu/data/moz.build
index 8eeb8741c814..bb7922c9fe8e 100644
--- a/config/external/icu/data/moz.build
+++ b/config/external/icu/data/moz.build
@@ -14,14 +14,25 @@ if CONFIG['OS_ARCH'] == 'WINNT':
 elif CONFIG['OS_ARCH'] == 'Darwin':
     ASFLAGS += ['-DPREFIX']
 
-ASFLAGS += [
+data_symbol = 'icudt%s_dat' % CONFIG['MOZ_ICU_VERSION']
+asflags = [
     '-DICU_DATA_FILE="%s"' % CONFIG['ICU_DATA_FILE'],
-    '-DICU_DATA_SYMBOL=icudt%s_dat' % CONFIG['MOZ_ICU_VERSION'],
+    '-DICU_DATA_SYMBOL=%s' % data_symbol,
 ]
 LOCAL_INCLUDES += ['.']
 
-if CONFIG['HAVE_YASM']:
+if CONFIG['OS_TARGET'] == 'WINNT' and CONFIG['CPU_ARCH'] == 'aarch64':
+    icudata = 'icudata.asm'
+    GENERATED_FILES += [icudata]
+    SOURCES += ['!%s' % icudata]
+    icudata = GENERATED_FILES[icudata]
+    icudata.script = 'genicudata.py'
+    icudata.inputs = [CONFIG['ICU_DATA_FILE']]
+    icudata.flags = [data_symbol]
+elif CONFIG['HAVE_YASM']:
     USE_YASM = True
     SOURCES += ['icudata.s']
+    ASFLAGS += asflags
 elif CONFIG['GNU_AS']:
     SOURCES += ['icudata_gas.S']
+    ASFLAGS += asflags