diff --git a/lang/bytecode.c b/lang/bytecode.c
index dcb4b3d..bebd129 100644
--- a/lang/bytecode.c
+++ b/lang/bytecode.c
@@ -10,7 +10,7 @@
 
 // Opcode definitions, see bytecode_run for further documentation
 enum opcodes {
-	// 0x00 is unused
+	OP_END = 0x00,
 	OP_NUM = 0x01,
 	OP_RET = 0x03,
 	// 0x02 was an earlier variant of OP_DROP
@@ -23,10 +23,12 @@
 	OP_SELF = 0x0A
 };
 
+#include <stdio.h>
+
 void bytecode_run(VmState state, Object obj, const unsigned char *bytecode) {
 	const unsigned char *pos_code = &bytecode[0];
-	unsigned char op = OP_RET;
-	while ((op = *pos_code++) != OP_RET) {
+	unsigned char op = OP_END;
+	while ((op = *pos_code++) != OP_END) {
 		switch (op) {
 		// OP_NUM pushes a number on to the stack
 		// First argument is a 4-byte little endian number
@@ -92,9 +94,15 @@
 			vm_stack_push(state, obj);
 			break;
 		}
+		// OP_RET returns
+		case OP_RET: {
+			return;
+		}
 		// Unknown op, error out
 		default:
 			abort_msg("bytecode_run: Unknown op");
 		}
 	}
+	// Uh-oh, no more bytecode?
+	abort_msg("bytecode_run: Ran out of bytecode to run!");
 }
diff --git a/lang/compile.py b/lang/compile.py
index c386064..560bd50 100755
--- a/lang/compile.py
+++ b/lang/compile.py
@@ -429,6 +429,7 @@
 		else:
 			print("Unknown bytecode node: %s" % (node))
 			return None
+	bytes += b"\x00" # OP_END
 	return bytes
 
 ## C file output