diff --git a/t/t0050-filesystem.sh b/t/t0050-filesystem.sh
index 057c97c49..1542cf6a1 100755
--- a/t/t0050-filesystem.sh
+++ b/t/t0050-filesystem.sh
@@ -4,8 +4,8 @@ test_description='Various filesystem issues'
 
 . ./test-lib.sh
 
-auml=`printf '\xc3\xa4'`
-aumlcdiar=`printf '\x61\xcc\x88'`
+auml=$(printf '\303\244')
+aumlcdiar=$(printf '\141\314\210')
 
 case_insensitive=
 unibad=
diff --git a/t/t3419-rebase-patch-id.sh b/t/t3419-rebase-patch-id.sh
index 1aee48351..bd8efaf00 100755
--- a/t/t3419-rebase-patch-id.sh
+++ b/t/t3419-rebase-patch-id.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 test_description='git rebase - test patch id computation'
 
@@ -27,7 +27,7 @@ scramble()
 		then
 			echo "$x"
 		fi
-		i=$(((i+1) % 10))
+		i=$((($i+1) % 10))
 	done < "$1" > "$1.new"
 	mv -f "$1.new" "$1"
 }