diff --git a/src/target/cortexm.c b/src/target/cortexm.c
index 59fce89d..80e1caf6 100644
--- a/src/target/cortexm.c
+++ b/src/target/cortexm.c
@@ -633,10 +633,17 @@ int cortexm_run_stub(target *t, uint32_t loadaddr,
 		return -1;
 
 	/* Execute the stub */
+	enum target_halt_reason reason;
 	cortexm_halt_resume(t, 0);
-	while (!cortexm_halt_poll(t, NULL))
+	while ((reason = cortexm_halt_poll(t, NULL)) == TARGET_HALT_RUNNING)
 		;
 
+	if (reason == TARGET_HALT_ERROR)
+		raise_exception(EXCEPTION_ERROR, "Target lost in stub");
+
+	if (reason != TARGET_HALT_BREAKPOINT)
+		return -2;
+
 	uint32_t pc = cortexm_pc_read(t);
 	uint16_t bkpt_instr = target_mem_read16(t, pc);
 	if (bkpt_instr >> 8 != 0xbe)