diff --git a/bootstrap/ISBPL.java b/bootstrap/ISBPL.java
index dfc3dfa..5282c5b 100644
--- a/bootstrap/ISBPL.java
+++ b/bootstrap/ISBPL.java
@@ -15,6 +15,10 @@ import java.util.function.Supplier;
  */
 
 public class ISBPL {
+    // TODO: fully implement JIO
+    // public static final boolean ENABLE_JINTEROP = true;
+
+
     static boolean debug = false;
     public ISBPLDebugger.IPC debuggerIPC = new ISBPLDebugger.IPC();
     ArrayList<ISBPLType> types = new ArrayList<>();
@@ -846,6 +850,15 @@ public class ISBPL {
                     }
                 };
                 break;
+            case "def":
+                func = (stack) -> {
+                    ISBPLObject str = stack.pop();
+                    ISBPLObject callable = stack.pop();
+                    String s = toJavaString(str);
+                    callable.checkType(getType("func"));
+                    addFunction(s, (ISBPLCallable) callable.object);
+                };
+                break;
             default:
                 func = natives.get(name);
                 break;
diff --git a/std.isbpl b/std.isbpl
index ecf04e2..fc94e3d 100644
--- a/std.isbpl
+++ b/std.isbpl
@@ -64,6 +64,7 @@ native %
 native ^
 
 native fcall
+native def
 
 func ++ { 1 + }
 func -- { 1 - }