diff --git a/bsc/BSC_Tests.ttcn b/bsc/BSC_Tests.ttcn
index 87e0d0869..1b37f78cd 100644
--- a/bsc/BSC_Tests.ttcn
+++ b/bsc/BSC_Tests.ttcn
@@ -6918,7 +6918,7 @@ return template MobileAllocationLV {
 	}
 
 	/* Ensure that ma_mask is octet-aligned */
-	ma_mask := substr(ma_mask, 0, ma_mask_len + 1);
+	ma_mask := substr(ma_mask, 0, ma_mask_len);
 	ma_mask_len := (ma_mask_len + 8 - 1) / 8;
 	ma_mask := f_pad_bit(ma_mask, ma_mask_len * 8, '0'B);