diff --git a/src/charset.c b/src/charset.c
index bf5af37..4289360 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -1594,6 +1594,12 @@
     return (c == '0' || c == '1');
 }
 
+    static int
+vim_isodigit(int c)
+{
+    return (c >= '0' && c <= '7');
+}
+
 /*
  * Vim's own character class functions.  These exist because many library
  * islower()/toupper() etc. do not work properly: they crash when used with
@@ -1831,7 +1837,7 @@
 	    // binary
 	    ptr += 2;
 	else if ((what & STR2NR_OOCT)
-		&& (pre == 'O' || pre == 'o') && vim_isbdigit(ptr[2])
+		&& (pre == 'O' || pre == 'o') && vim_isodigit(ptr[2])
 		&& (maxlen == 0 || maxlen > 2))
 	    // octal with prefix "0o"
 	    ptr += 2;
diff --git a/src/testdir/test_eval_stuff.vim b/src/testdir/test_eval_stuff.vim
index 316fb42..e5f521c 100644
--- a/src/testdir/test_eval_stuff.vim
+++ b/src/testdir/test_eval_stuff.vim
@@ -218,6 +218,7 @@
   call assert_equal(15, 0o17)
   call assert_equal(15, 0O17)
   call assert_equal(18, 018)
+  call assert_equal(511, 0o777)
   call assert_equal(64, 0b1'00'00'00)
   call assert_equal(1048576, 0x10'00'00)
   call assert_equal(32768, 0o10'00'00)
@@ -233,6 +234,7 @@
   call assert_equal(15, 0o17)
   call assert_equal(15, 0O17)
   call assert_equal(18, 018)
+  call assert_equal(511, 0o777)
 endfunc
 
 func Test_scriptversion_fail()
diff --git a/src/version.c b/src/version.c
index f39a0d3..f4a1d58 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2309,
+/**/
     2308,
 /**/
     2307,