diff --git a/src/nvim/regexp.c b/src/nvim/regexp.c
index a70b150e9b..b7fc39fdb3 100644
--- a/src/nvim/regexp.c
+++ b/src/nvim/regexp.c
@@ -772,7 +772,7 @@ static int get_equi_class(char_u **pp)
   int l = 1;
   char_u      *p = *pp;
 
-  if (p[1] == '=') {
+  if (p[1] == '=' && p[2] != NUL) {
     l = (*mb_ptr2len)(p + 2);
     if (p[l + 2] == '=' && p[l + 3] == ']') {
       c = utf_ptr2char(p + 2);
diff --git a/src/nvim/testdir/test_regexp_latin.vim b/src/nvim/testdir/test_regexp_latin.vim
index e31bb08b19..adbded128f 100644
--- a/src/nvim/testdir/test_regexp_latin.vim
+++ b/src/nvim/testdir/test_regexp_latin.vim
@@ -38,3 +38,10 @@ func Test_range_with_newline()
   call assert_equal(0, search("[ -*\\t-\\n]"))
   bwipe!
 endfunc
+
+func Test_get_equi_class()
+  new
+  " Incomplete equivalence class caused invalid memory access
+  s/^/[[=
+  call assert_equal(1, search(getline(1)))
+endfunc