diff --git a/src/rk65c02.c b/src/rk65c02.c
index 4960e43..2a766a8 100644
--- a/src/rk65c02.c
+++ b/src/rk65c02.c
@@ -32,6 +32,7 @@ rk65c02_init(bus_t *b)
 
 	e.bps_head = NULL;
 	e.trace_head = NULL;
+	e.runtime_disassembly = false;
 
 	return e;
 }
@@ -103,8 +104,8 @@ rk65c02_exec(rk65c02emu_t *e)
 		return;
 	}
 
-	/* if disassembly-when-running enabled */
-	disassemble(e->bus, e->regs.PC);
+	if (e->runtime_disassembly)
+		disassemble(e->bus, e->regs.PC);
 
 	i = instruction_fetch(e->bus, e->regs.PC);
 	id = instruction_decode(i.opcode);
diff --git a/src/rk65c02.h b/src/rk65c02.h
index d5b4479..53df0ec 100644
--- a/src/rk65c02.h
+++ b/src/rk65c02.h
@@ -69,7 +69,7 @@ struct rk65c02emu {
 	bool irq;		/* interrupt request line state, true is asserted */
 
 	breakpoint_t *bps_head;	/* pointer to linked list with breakpoints  */
-
+	bool runtime_disassembly; /* disassemble code when emulator is running */
 	bool trace;		/* tracing mode enable/disable */
 	trace_t *trace_head;	/* pointer to linked list with trace log */
 };