diff --git a/intel_mips/base-files/lib/functions/iopsys-environment.sh b/intel_mips/base-files/lib/functions/iopsys-environment.sh
index 97c0762d494ca452765ff4faab83de8fb93963db..cc5cfb36a379a3d80c961469743e309b19bec7d9 100644
--- a/intel_mips/base-files/lib/functions/iopsys-environment.sh
+++ b/intel_mips/base-files/lib/functions/iopsys-environment.sh
@@ -1,5 +1,5 @@
 get_base_macaddr() {
-	local basemac="$(fw_printenv -n ethaddr | tr ' ' ':' | sed 's/:$//' | tr [a-z] [A-Z])"
+	local basemac="$(fw_printenv -n ethaddr | tr ' ' ':' | sed 's/:$//' | tr 'a-z' 'A-Z')"
 	echo "$basemac"
 }
 
diff --git a/iopsys-brcm63xx-arm/base-files/lib/functions/iopsys-environment.sh b/iopsys-brcm63xx-arm/base-files/lib/functions/iopsys-environment.sh
index 6a5b185a0a6a75d08156df2c917fd628d4aacb20..2401626488c7eff3ebee6cb2947da266e4cdf9c8 100644
--- a/iopsys-brcm63xx-arm/base-files/lib/functions/iopsys-environment.sh
+++ b/iopsys-brcm63xx-arm/base-files/lib/functions/iopsys-environment.sh
@@ -1,5 +1,5 @@
 get_base_macaddr() {
-	local basemac="$(fw_printenv -n ethaddr | tr ' ' ':' | sed 's/:$//' | tr [a-z] [A-Z])"
+	local basemac="$(fw_printenv -n ethaddr | tr ' ' ':' | sed 's/:$//' | tr 'a-z' 'A-Z')"
 	echo "$basemac"
 }
 
diff --git a/iopsys-econet/base-files/lib/functions/iopsys-environment.sh b/iopsys-econet/base-files/lib/functions/iopsys-environment.sh
index 391b06ff201a763c9f38a3ae8b5223183ceb5948..7be97c494f26e86cd6633f8909eb0fc04ca5e75a 100644
--- a/iopsys-econet/base-files/lib/functions/iopsys-environment.sh
+++ b/iopsys-econet/base-files/lib/functions/iopsys-environment.sh
@@ -1,5 +1,5 @@
 get_base_macaddr() {
-	local basemac="$(fw_printenv -n ethaddr | tr ' ' ':' | sed 's/:$//' | tr [a-z] [A-Z])"
+	local basemac="$(fw_printenv -n ethaddr | tr ' ' ':' | sed 's/:$//' | tr 'a-z' 'A-Z')"
 	echo "$basemac"
 }
 
diff --git a/iopsys-ramips/mt7621/base-files/lib/functions/iopsys-environment.sh b/iopsys-ramips/mt7621/base-files/lib/functions/iopsys-environment.sh
index 417e6d07caa2a8256ce480e8f61d0d92da83aba4..dfca6aa9d355bb2df8b3643750048089a7e38451 100644
--- a/iopsys-ramips/mt7621/base-files/lib/functions/iopsys-environment.sh
+++ b/iopsys-ramips/mt7621/base-files/lib/functions/iopsys-environment.sh
@@ -1,5 +1,5 @@
 get_base_macaddr() {
-	local basemac="$(fw_printenv -n ethaddr | tr ' ' ':' | sed 's/:$//' | tr [a-z] [A-Z])"
+	local basemac="$(fw_printenv -n ethaddr | tr ' ' ':' | sed 's/:$//' | tr 'a-z' 'A-Z')"
 	echo "$basemac"
 }