diff --git a/tcl/target/stm32l0.cfg b/tcl/target/stm32l0.cfg
index ec5d5463e..e09af8001 100644
--- a/tcl/target/stm32l0.cfg
+++ b/tcl/target/stm32l0.cfg
@@ -61,10 +61,13 @@ proc stm32l0_enable_HSI16 {} {
 	echo "STM32L0: Enabling HSI16"
 
 	# Set HSI16ON in RCC_CR (leave MSI enabled)
-	mww 0x40021000 0x00000101
+    mmw 0x40021000 0x00000101 0
 
 	# Set HSI16 as SYSCLK (RCC_CFGR)
-	mww 0x4002100c 0x00000001
+	mmw 0x4002100c 0x00000001 0
+
+	# Wait until System clock switches to HSI16
+	while { ([ mrw 0x4002100c ] & 0x0c) != 0x04 } { }
 
 	# Increase speed
 	adapter_khz 2500
diff --git a/tcl/target/stm32l1.cfg b/tcl/target/stm32l1.cfg
index 054fa9b74..0933151a0 100644
--- a/tcl/target/stm32l1.cfg
+++ b/tcl/target/stm32l1.cfg
@@ -73,10 +73,10 @@ proc stm32l_enable_HSI {} {
 	echo "STM32L: Enabling HSI"
 
 	# Set HSION in RCC_CR
-	mww 0x40023800 0x00000101
+	mmw 0x40023800 0x00000101 0
 
 	# Set HSI as SYSCLK
-	mww 0x40023808 0x00000001
+	mmw 0x40023808 0x00000001 0
 
 	# Increase JTAG speed
 	adapter_khz 2000