diff --git a/browser/installer/Makefile.in b/browser/installer/Makefile.in
index 2e34a7746459..3d9389f829ed 100644
--- a/browser/installer/Makefile.in
+++ b/browser/installer/Makefile.in
@@ -141,9 +141,6 @@ endif
 endif
 DEFINES += -DLPROJ_ROOT=$(LPROJ_ROOT)
 
-ifdef MOZ_SYSTEM_ICU
-DEFINES += -DMOZ_SYSTEM_ICU
-endif
 ifdef CLANG_CXX
 DEFINES += -DCLANG_CXX
 endif
diff --git a/build/autoconf/icu.m4 b/build/autoconf/icu.m4
index 32fc84f30dd9..f1607575f3b9 100644
--- a/build/autoconf/icu.m4
+++ b/build/autoconf/icu.m4
@@ -17,6 +17,7 @@ if test -n "$MOZ_SYSTEM_ICU"; then
     PKG_CHECK_MODULES(MOZ_ICU, icu-i18n >= 59.1)
     CFLAGS="$CFLAGS $MOZ_ICU_CFLAGS"
     CXXFLAGS="$CXXFLAGS $MOZ_ICU_CFLAGS"
+    AC_DEFINE(MOZ_SYSTEM_ICU)
 fi
 
 AC_SUBST(MOZ_SYSTEM_ICU)
diff --git a/config/moz.build b/config/moz.build
index a990abb81b6d..d9c28fe54d05 100644
--- a/config/moz.build
+++ b/config/moz.build
@@ -26,9 +26,6 @@ if CONFIG['HOST_OS_ARCH'] != 'WINNT':
     ]
     HostProgram('nsinstall_real')
 
-if CONFIG['MOZ_SYSTEM_ICU']:
-    DEFINES['MOZ_SYSTEM_ICU'] = True
-
 PYTHON_UNITTEST_MANIFESTS += [
     'tests/python.ini',
 ]