diff --git a/read-cache.c b/read-cache.c
index 01a0e25051..5790a91044 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1249,9 +1249,9 @@ static void convert_from_disk(struct ondisk_cache_entry *ondisk, struct cache_en
 
 static inline size_t estimate_cache_size(size_t ondisk_size, unsigned int entries)
 {
-	long per_entry;
-
-	per_entry = sizeof(struct cache_entry) - sizeof(struct ondisk_cache_entry);
+	size_t fix_size_mem = offsetof(struct cache_entry, name);
+	size_t fix_size_dsk = offsetof(struct ondisk_cache_entry, name);
+	long per_entry = (fix_size_mem - fix_size_dsk + 7) & ~7;
 
 	/*
 	 * Alignment can cause differences. This should be "alignof", but
diff --git a/t/t7511-status-index.sh b/t/t7511-status-index.sh
new file mode 100755
index 0000000000..bca359dc1e
--- /dev/null
+++ b/t/t7511-status-index.sh
@@ -0,0 +1,50 @@
+#!/bin/sh
+
+test_description='git status with certain file name lengths'
+
+. ./test-lib.sh
+
+files="0 1 2 3 4 5 6 7 8 9 a b c d e f g h i j k l m n o p q r s t u v w x y z"
+
+check() {
+	len=$1
+	prefix=$2
+
+	for i in $files
+	do
+		: >$prefix$i
+	done
+
+	test_expect_success "status, filename length $len" "
+		git add $prefix* &&
+		git status
+	"
+	rm $prefix* .git/index
+}
+
+check  1
+check  2 p
+check  3 pr
+check  4 pre
+check  5 pref
+check  6 prefi
+check  7 prefix
+check  8 prefix-
+check  9 prefix-p
+check 10 prefix-pr
+check 11 prefix-pre
+check 12 prefix-pref
+check 13 prefix-prefi
+check 14 prefix-prefix
+check 15 prefix-prefix-
+check 16 prefix-prefix-p
+check 17 prefix-prefix-pr
+check 18 prefix-prefix-pre
+check 19 prefix-prefix-pref
+check 20 prefix-prefix-prefi
+check 21 prefix-prefix-prefix
+check 22 prefix-prefix-prefix-
+check 23 prefix-prefix-prefix-p
+check 24 prefix-prefix-prefix-pr
+
+test_done