diff --git a/t/lib-pack.sh b/t/lib-pack.sh
index 7e8685b44c..b96e1254dd 100644
--- a/t/lib-pack.sh
+++ b/t/lib-pack.sh
@@ -12,10 +12,10 @@
 # Print the big-endian 4-byte octal representation of $1
 uint32_octal () {
 	n=$1
-	printf '\%o' $(($n / 16777216)); n=$((n % 16777216))
-	printf '\%o' $(($n /    65536)); n=$((n %    65536))
-	printf '\%o' $(($n /      256)); n=$((n %      256))
-	printf '\%o' $(($n           ));
+	printf '\\%o' $(($n / 16777216)); n=$((n % 16777216))
+	printf '\\%o' $(($n /    65536)); n=$((n %    65536))
+	printf '\\%o' $(($n /      256)); n=$((n %      256))
+	printf '\\%o' $(($n           ));
 }
 
 # Print the big-endian 4-byte binary representation of $1