diff --git a/functions.sh.in b/functions.sh.in
index 7b00980618df71cf50a36b2d44752d4b729ae2b2..189a67f78b82c1cd246ade0d77c3c68041de74f5 100644
--- a/functions.sh.in
+++ b/functions.sh.in
@@ -273,6 +273,26 @@ error2() {
 	printf "           %s\n" "$1" >&2
 }
 
+lowercase() {
+	str=$1
+	for pair in Aa Bb Cc Dd Ee Ff Gg Hh Ii Jj Kk Ll Mm Nn Oo Pp Qq Rr Ss Tt Uu Vv Ww Xx Yy Zz; do
+		orig=${pair:0:1}
+		repl=${pair:1:1}
+		str=${str//"$orig"/"$repl"}
+	done
+	echo "$str"
+}
+
+uppercase() {
+	str=$1
+	for pair in aA bB cC dD eE fF gG hH iI jJ kK lL mM nN oO pP qQ rR sS tT uU vV wW xX yY zZ; do
+		orig=${pair:0:1}
+		repl=${pair:1:1}
+		str=${str//"$orig"/"$repl"}
+	done
+	echo "$str"
+}
+
 set_xterm_title() {
 	if [ "$TERM" = xterm ] && [ -n "$USE_COLORS" ]; then
 		 printf "\033]0;$1\007" >&2
diff --git a/tests/functions_test b/tests/functions_test
index fd6e59436aec1854cc60c25b3bd3c8a4ec9ef183..8665895a569d691f4706ca06aa828e6dcdb4f5e8 100755
--- a/tests/functions_test
+++ b/tests/functions_test
@@ -7,7 +7,9 @@ init_tests \
 	funcs_check_missing_apk \
 	funcs_check_missing_git \
 	funcs_check_env_set_but_empty \
-	funcs_check_defconfig
+	funcs_check_defconfig \
+	funcs_check_lowercase \
+	funcs_check_uppercase
 
 FUNCS=$(atf_get_srcdir)/../functions.sh
 
@@ -85,3 +87,15 @@ funcs_check_defconfig_body() {
 		-o match:"envcflags" \
 		sh -e -c " . $FUNCS; echo \"\$CFLAGS\""
 }
+
+funcs_check_lowercase_body() {
+	atf_check \
+		-o match:"aabcdefghijklkmnopqrstuvwxyz" \
+		sh -e -c " . $FUNCS; lowercase 'AABCDEFGHIJKLKMNOPQRSTUVWXYZ'"
+}
+
+funcs_check_uppercase_body() {
+	atf_check \
+		-o match:"AABCDEFGHIJKLKMNOPQRSTUVWXYZ" \
+		sh -e -c " . $FUNCS; uppercase 'aabcdefghijklkmnopqrstuvwxyz'"
+}