diff --git a/lib/ex.coffee b/lib/ex.coffee
index e259c90..684b2f6 100644
--- a/lib/ex.coffee
+++ b/lib/ex.coffee
@@ -199,9 +199,9 @@ class Ex
   substitute: (range, args) ->
     args = args.trimLeft()
     delim = args[0]
-    if /[a-z]/i.test(delim)
+    if /[a-z1-9\\"|]/i.test(delim)
       throw new CommandError(
-        "Regular expressions can't be delimited by letters")
+        "Regular expressions can't be delimited by alphanumeric characters, '\\', '\"' or '|'")
     delimRE = new RegExp("[^\\\\]#{delim}")
     spl = []
     args_ = args[1..]
diff --git a/spec/ex-commands-spec.coffee b/spec/ex-commands-spec.coffee
index 803aa57..a4813b5 100644
--- a/spec/ex-commands-spec.coffee
+++ b/spec/ex-commands-spec.coffee
@@ -449,12 +449,19 @@ describe "the commands", ->
       submitNormalModeInputText(':%substitute/abc/ghi/ig')
       expect(editor.getText()).toEqual('ghiaghi\ndefdDEF\nghiaghi')
 
-    it "can't be delimited by letters", ->
-      keydown(':')
-      submitNormalModeInputText(':substitute nanxngi')
-      expect(atom.notifications.notifications[0].message).toEqual(
-        "Command error: Regular expressions can't be delimited by letters")
-      expect(editor.getText()).toEqual('abcaABC\ndefdDEF\nabcaABC')
+    describe "illegal delimiters", ->
+      test = (delim) ->
+        keydown(':')
+        submitNormalModeInputText(":substitute #{delim}a#{delim}x#{delim}gi")
+        expect(atom.notifications.notifications[0].message).toEqual(
+          "Command error: Regular expressions can't be delimited by alphanumeric characters, '\\', '\"' or '|'")
+        expect(editor.getText()).toEqual('abcaABC\ndefdDEF\nabcaABC')
+
+      it "can't be delimited by letters", -> test 'n'
+      it "can't be delimited by numbers", -> test '3'
+      it "can't be delimited by '\\'",    -> test '\\'
+      it "can't be delimited by '\"'",    -> test '"'
+      it "can't be delimited by '|'",     -> test '|'
 
     describe "capturing groups", ->
       beforeEach ->