diff --git a/haxetool/core.js b/haxetool/core.js
index 42c6dfa..763a072 100644
--- a/haxetool/core.js
+++ b/haxetool/core.js
@@ -29,6 +29,7 @@ class Config {
         this.assets = [];
         this.libs = [];
         this.macros = [];
+        this.flags = [];
         this.icon = null;
         this.meta = {
             title: null,
@@ -57,6 +58,7 @@ class Config {
         if (params.assets !== undefined) this.assets = this.assets.concat(params.assets.map(Config.absolutePath));
         if (params.libs !== undefined) this.libs = this.libs.concat(Array.isArray(params.libs) ? params.libs : Object.entries(params.libs).map(([k, v]) => ({name: k, version: v})));
         if (params.macros !== undefined) this.macros = this.macros.concat(params.macros);
+        if (params.flags !== undefined) this.flags = this.flags.concat(params.flags);
         if (params.meta !== undefined) this.meta = {...this.meta, ...params.meta};
         if (this.meta.icon) this.icon = Config.absolutePath(this.meta.icon);
     }
diff --git a/template/project.xml b/template/project.xml
index 0a7e1bb..bbd63c1 100644
--- a/template/project.xml
+++ b/template/project.xml
@@ -11,6 +11,8 @@
     <haxelib name="<%=item.name%>" version="<%=item.version.split('@').shift()%>"/><% }); %>
     <% macros.forEach(function(item) { %>
     <haxeflag name="--macro" value="<%=item%>"/><% }); %>
+    <% flags.forEach(function(item) { %>
+    <haxeflag name="-D" value="<%=item%>"/><% }); %>
 
     <window fps="30"/>
     <window width="1024" height="768" unless="html5"/>