diff --git a/t/t4041-diff-submodule-option.sh b/t/t4041-diff-submodule-option.sh
index 4d4aa1650f..4dd4954260 100755
--- a/t/t4041-diff-submodule-option.sh
+++ b/t/t4041-diff-submodule-option.sh
@@ -37,8 +37,12 @@ add_file () {
 			test_tick &&
 			# "git commit -m" would break MinGW, as Windows refuse to pass
 			# $test_encoding encoded parameter to git.
-			echo "Add $name ($added $name)" | iconv -f utf-8 -t $test_encoding |
-			git -c "i18n.commitEncoding=$test_encoding" commit -F -
+			message="Add $name ($added $name)" &&
+			if test_have_prereq ICONV
+			then
+				message=$(echo "$message" | iconv -f utf-8 -t $test_encoding)
+			fi &&
+			echo "$message" | git -c "i18n.commitEncoding=$test_encoding" commit -F -
 		done >/dev/null &&
 		git rev-parse --short --verify HEAD
 	)
diff --git a/t/t4059-diff-submodule-not-initialized.sh b/t/t4059-diff-submodule-not-initialized.sh
index 0fe81056d5..bb902ce94d 100755
--- a/t/t4059-diff-submodule-not-initialized.sh
+++ b/t/t4059-diff-submodule-not-initialized.sh
@@ -35,8 +35,12 @@ add_file () {
 			test_tick &&
 			# "git commit -m" would break MinGW, as Windows refuse to pass
 			# $test_encoding encoded parameter to git.
-			echo "Add $name ($added $name)" | iconv -f utf-8 -t $test_encoding |
-			git -c "i18n.commitEncoding=$test_encoding" commit -F -
+			message="Add $name ($added $name)" &&
+			if test_have_prereq ICONV
+			then
+				message=$(echo "$message" | iconv -f utf-8 -t $test_encoding)
+			fi &&
+			echo "$message" | git -c "i18n.commitEncoding=$test_encoding" commit -F -
 		done >/dev/null &&
 		git rev-parse --short --verify HEAD
 	)
diff --git a/t/t4060-diff-submodule-option-diff-format.sh b/t/t4060-diff-submodule-option-diff-format.sh
index dbfeb7470b..d8f9213255 100755
--- a/t/t4060-diff-submodule-option-diff-format.sh
+++ b/t/t4060-diff-submodule-option-diff-format.sh
@@ -35,8 +35,12 @@ add_file () {
 			test_tick &&
 			# "git commit -m" would break MinGW, as Windows refuse to pass
 			# $test_encoding encoded parameter to git.
-			echo "Add $name ($added $name)" | iconv -f utf-8 -t $test_encoding |
-			git -c "i18n.commitEncoding=$test_encoding" commit -F -
+			message="Add $name ($added $name)" &&
+			if test_have_prereq ICONV
+			then
+				message=$(echo "$message" | iconv -f utf-8 -t $test_encoding)
+			fi &&
+			echo "$message" | git -c "i18n.commitEncoding=$test_encoding" commit -F -
 		done >/dev/null &&
 		git rev-parse --short --verify HEAD
 	)