diff --git a/src/target/ch32f1.c b/src/target/ch32f1.c
index e6bfe64..3fe7e24 100644
--- a/src/target/ch32f1.c
+++ b/src/target/ch32f1.c
@@ -159,8 +159,10 @@ static int ch32f1_flash_lock(target *t)
 */
 bool ch32f1_probe(target *t)
 {
-	const uint32_t idcode = target_mem_read32(t, DBGMCU_IDCODE) & 0xfff;
-	if ((t->cpuid & CPUID_PARTNO_MASK) != CORTEX_M3 || idcode != 0x410) // only ch32f103
+	if ((t->cpuid & CPUID_PARTNO_MASK) != CORTEX_M3)
+		return false;
+	const uint32_t idcode = target_mem_read32(t, DBGMCU_IDCODE) & 0x00000fffU;
+	if (idcode != 0x410) // only ch32f103
 		return false;
 
 	// try to flock