diff --git a/src/regexp_nfa.c b/src/regexp_nfa.c
index 333c006..ba75834 100644
--- a/src/regexp_nfa.c
+++ b/src/regexp_nfa.c
@@ -1475,7 +1475,7 @@
 			    default:  nr = -1; break;
 			}
 
-			if (nr < 0)
+			if (nr < 0 || nr > INT_MAX)
 			    EMSG2_RET_FAIL(
 			       _("E678: Invalid character after %s%%[dxouU]"),
 				    reg_magic == MAGIC_ALL);
diff --git a/src/testdir/test_search.vim b/src/testdir/test_search.vim
index 972144a..4ff2aca 100644
--- a/src/testdir/test_search.vim
+++ b/src/testdir/test_search.vim
@@ -1211,3 +1211,12 @@
   call assert_equal(bufcontent[1], @/)
   call Incsearch_cleanup()
 endfunc
+
+func Test_large_hex_chars()
+  " This used to cause a crash, the character becomes an NFA state.
+  try
+    /\%Ufffffc23
+  catch
+    call assert_match('E678:', v:exception)
+  endtry
+endfunc
diff --git a/src/version.c b/src/version.c
index 825c5e5..13f54e3 100644
--- a/src/version.c
+++ b/src/version.c
@@ -780,6 +780,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    968,
+/**/
     967,
 /**/
     966,