diff --git a/project.gyp b/project.gyp
index f1efaeef..e015da08 100644
--- a/project.gyp
+++ b/project.gyp
@@ -105,6 +105,9 @@
       'cflags_c': [
         '-std=c99', '-U_FORTIFY_SOURCE', '-D_FORTIFY_SOURCE=1'
       ],
+      'defines': [
+        'UTFPROC_EXPORTS',
+      ],
       'ldflags': [
         '-g',
       ],