diff --git a/scripts/stm32_mem.py b/scripts/stm32_mem.py
index d30a855..732685c 100755
--- a/scripts/stm32_mem.py
+++ b/scripts/stm32_mem.py
@@ -89,7 +89,10 @@ def stm32_scan(args, test):
 		exit(-1)
 
 	for dev in devs:
-		dfudev = dfu.dfu_device(*dev)
+                try:
+                        dfudev = dfu.dfu_device(*dev)
+                except:
+                        return 0
 		man = dfudev.handle.getString(dfudev.dev.iManufacturer, 30)
 		if man == "Black Sphere Technologies": bmp = bmp + 1
 	if bmp == 0 :
diff --git a/src/target/cortexm.c b/src/target/cortexm.c
index 86e46fd..cbd769b 100644
--- a/src/target/cortexm.c
+++ b/src/target/cortexm.c
@@ -413,6 +413,8 @@ void cortexm_detach(target *t)
 
 	/* Disable debug */
 	target_mem_write32(t, CORTEXM_DHCSR, CORTEXM_DHCSR_DBGKEY);
+	/* Add some clock cycles to get the CPU running again.*/
+	target_mem_read32(t, 0);
 }
 
 enum { DB_DHCSR, DB_DCRSR, DB_DCRDR, DB_DEMCR };