diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 54fd9d326a..0f8d8b8d76 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -7197,11 +7197,9 @@ static void f_sha256(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 
   if (argvars[0].v_type == VAR_BLOB) {
     blob_T *blob = argvars[0].vval.v_blob;
-    if (blob != NULL) {
-      const uint8_t *p = (uint8_t *)blob->bv_ga.ga_data;
-      int len = blob->bv_ga.ga_len;
-      rettv->vval.v_string = xstrdup(sha256_bytes(p, (size_t)len, NULL, 0));
-    }
+    const uint8_t *p = blob != NULL ? (uint8_t *)blob->bv_ga.ga_data : (uint8_t *)"";
+    int len = blob != NULL ? blob->bv_ga.ga_len : 0;
+    rettv->vval.v_string = xstrdup(sha256_bytes(p, (size_t)len, NULL, 0));
   } else {
     const char *p = tv_get_string(&argvars[0]);
     const char *hash = sha256_bytes((const uint8_t *)p, strlen(p), NULL, 0);
diff --git a/test/old/testdir/test_sha256.vim b/test/old/testdir/test_sha256.vim
index 9f4599bd73..4c2380176e 100644
--- a/test/old/testdir/test_sha256.vim
+++ b/test/old/testdir/test_sha256.vim
@@ -5,24 +5,25 @@ source check.vim
 CheckFunction sha256
 
 function Test_sha256()
-  " test for empty string:
+  " tests for string:
+  " empty string
   call assert_equal('e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855', sha256(""))
-
-  "'test for 1 char:
+  " null string
+  call assert_equal('e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855', sha256(v:_null_string))
+  " string with 1 char
   call assert_equal('ca978112ca1bbdcafac231b39a23dc4da786eff8147c4e72b9807785afee48bb', sha256("a"))
-  "
-  "test for 3 chars:
+  " string with 3 chars
   call assert_equal('ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad', "abc"->sha256())
-
-  " test for contains meta char:
+  " string containing meta char
   call assert_equal('807eff6267f3f926a21d234f7b0cf867a86f47e07a532f15e8cc39ed110ca776', sha256("foo\nbar"))
-
-  " test for contains non-ascii char:
+  " string containing non-ascii char
   call assert_equal('5f78c33274e43fa9de5659265c1d917e25c03722dcb0b8d27db8d5feaa813953', sha256("\xde\xad\xbe\xef"))
 
-  " test for blob:
+  " tests for blob:
   " empty blob
   call assert_equal('e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855', sha256(0z))
+  " null blob
+  call assert_equal('e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855', sha256(v:_null_blob))
   " blob with single byte
   call assert_equal('ca978112ca1bbdcafac231b39a23dc4da786eff8147c4e72b9807785afee48bb', sha256(0z61))
   " blob with "abc"