diff --git a/autoload/vimlparser.vim b/autoload/vimlparser.vim
index ab17030..25db0a4 100644
--- a/autoload/vimlparser.vim
+++ b/autoload/vimlparser.vim
@@ -1509,13 +1509,15 @@ function! s:VimLParser.parse_cmd_call() abort
   call self.add_node(node)
 endfunction
 
-function! s:VimLParser.parse_heredoc() abort
+function! s:VimLParser.parse_heredoc(prefix) abort
   let node = s:Node(s:NODE_HEREDOC)
   let node.pos = self.ea.cmdpos
   let node.op = ''
   let node.rlist = []
   let node.body = []
 
+  " allow prefix to precede heredoc end marker if true
+  let is_trim = s:FALSE
   while s:TRUE
     call self.reader.skip_white()
     let pos = self.reader.getpos()
@@ -1531,6 +1533,9 @@ function! s:VimLParser.parse_heredoc() abort
       let keynode.pos = pos
       let keynode.value = key
       call add(node.rlist, keynode)
+      if key ==# 'trim'
+        let is_trim = s:TRUE
+      endif
     endif
   endwhile
   if node.op ==# ''
@@ -1543,7 +1548,7 @@ function! s:VimLParser.parse_heredoc() abort
     endif
     let pos = self.reader.getpos()
     let line = self.reader.getn(-1)
-    if line ==# node.op
+    if line ==# node.op || is_trim && line ==# a:prefix . node.op
       return node
     endif
     let linenode = s:Node(s:NODE_STRING)
@@ -1600,7 +1605,31 @@ function! s:VimLParser.parse_cmd_let() abort
     call self.reader.getn(len(s2))
     call self.reader.skip_white()
     let node.op = s2
-    let node.right = self.parse_heredoc()
+
+    " compute allowed prefix for heredoc end marker (e.g. EOF)
+    let pos = self.reader.tell()
+    while self.reader.tell() > 0
+      if self.reader.peek() ==# '<EOL>'
+        call self.reader.seek_cur(1)
+        break
+      endif
+      call self.reader.seek_cur(-1)
+    endwhile
+    let prefix = ''
+    while s:TRUE
+      let c = self.reader.getn(1)
+      if c ==# ':'
+        " any presence of leading ':' disables prefix for heredoc end marker
+        let prefix = ''
+        break
+      elseif !s:iswhite(c)
+        break
+      endif
+      let prefix .= c
+    endwhile
+    call self.reader.seek_set(pos)
+
+    let node.right = self.parse_heredoc(prefix)
     call self.add_node(node)
     return
   elseif s1 ==# '='
diff --git a/js/vimlparser.js b/js/vimlparser.js
index 1efd4f3..91fc9c0 100644
--- a/js/vimlparser.js
+++ b/js/vimlparser.js
@@ -1805,12 +1805,14 @@ VimLParser.prototype.parse_cmd_call = function() {
     this.add_node(node);
 }
 
-VimLParser.prototype.parse_heredoc = function() {
+VimLParser.prototype.parse_heredoc = function(prefix) {
     var node = Node(NODE_HEREDOC);
     node.pos = this.ea.cmdpos;
     node.op = "";
     node.rlist = [];
     node.body = [];
+    // allow prefix to precede heredoc end marker if true
+    var is_trim = FALSE;
     while (TRUE) {
         this.reader.skip_white();
         var pos = this.reader.getpos();
@@ -1827,6 +1829,9 @@ VimLParser.prototype.parse_heredoc = function() {
             keynode.pos = pos;
             keynode.value = key;
             viml_add(node.rlist, keynode);
+            if (key == "trim") {
+                var is_trim = TRUE;
+            }
         }
     }
     if (node.op == "") {
@@ -1839,7 +1844,7 @@ VimLParser.prototype.parse_heredoc = function() {
         }
         var pos = this.reader.getpos();
         var line = this.reader.getn(-1);
-        if (line == node.op) {
+        if (line == node.op || is_trim && line == prefix + node.op) {
             return node;
         }
         var linenode = Node(NODE_STRING);
@@ -1894,7 +1899,30 @@ VimLParser.prototype.parse_cmd_let = function() {
         this.reader.getn(viml_len(s2));
         this.reader.skip_white();
         node.op = s2;
-        node.right = this.parse_heredoc();
+        // compute allowed prefix for heredoc end marker (e.g. EOF)
+        var pos = this.reader.tell();
+        while (this.reader.tell() > 0) {
+            if (this.reader.peek() == "<EOL>") {
+                this.reader.seek_cur(1);
+                break;
+            }
+            this.reader.seek_cur(-1);
+        }
+        var prefix = "";
+        while (TRUE) {
+            var c = this.reader.getn(1);
+            if (c == ":") {
+                // any presence of leading ':' disables prefix for heredoc end marker
+                var prefix = "";
+                break;
+            }
+            else if (!iswhite(c)) {
+                break;
+            }
+            prefix += c;
+        }
+        this.reader.seek_set(pos);
+        node.right = this.parse_heredoc(prefix);
         this.add_node(node);
         return;
     }
diff --git a/py/vimlparser.py b/py/vimlparser.py
index 74011da..f0562b6 100644
--- a/py/vimlparser.py
+++ b/py/vimlparser.py
@@ -1483,12 +1483,14 @@ def parse_cmd_call(self):
             raise VimLParserException(Err("Not an function call", node.left.pos))
         self.add_node(node)
 
-    def parse_heredoc(self):
+    def parse_heredoc(self, prefix):
         node = Node(NODE_HEREDOC)
         node.pos = self.ea.cmdpos
         node.op = ""
         node.rlist = []
         node.body = []
+        # allow prefix to precede heredoc end marker if true
+        is_trim = FALSE
         while TRUE:
             self.reader.skip_white()
             pos = self.reader.getpos()
@@ -1503,6 +1505,8 @@ def parse_heredoc(self):
                 keynode.pos = pos
                 keynode.value = key
                 viml_add(node.rlist, keynode)
+                if key == "trim":
+                    is_trim = TRUE
         if node.op == "":
             raise VimLParserException(Err("E172: Missing marker", self.reader.getpos()))
         self.parse_trail()
@@ -1511,7 +1515,7 @@ def parse_heredoc(self):
                 break
             pos = self.reader.getpos()
             line = self.reader.getn(-1)
-            if line == node.op:
+            if line == node.op or is_trim and line == prefix + node.op:
                 return node
             linenode = Node(NODE_STRING)
             linenode.pos = pos
@@ -1558,7 +1562,25 @@ def parse_cmd_let(self):
             self.reader.getn(viml_len(s2))
             self.reader.skip_white()
             node.op = s2
-            node.right = self.parse_heredoc()
+            # compute allowed prefix for heredoc end marker (e.g. EOF)
+            pos = self.reader.tell()
+            while self.reader.tell() > 0:
+                if self.reader.peek() == "<EOL>":
+                    self.reader.seek_cur(1)
+                    break
+                self.reader.seek_cur(-1)
+            prefix = ""
+            while TRUE:
+                c = self.reader.getn(1)
+                if c == ":":
+                    # any presence of leading ':' disables prefix for heredoc end marker
+                    prefix = ""
+                    break
+                elif not iswhite(c):
+                    break
+                prefix += c
+            self.reader.seek_set(pos)
+            node.right = self.parse_heredoc(prefix)
             self.add_node(node)
             return
         elif s1 == "=":
diff --git a/test/test_heredoc.ok b/test/test_heredoc.ok
index 0de3f6b..b995189 100644
--- a/test/test_heredoc.ok
+++ b/test/test_heredoc.ok
@@ -1,3 +1,12 @@
 (let =<< a (heredoc (list) "EOS" (list "hello" " world")))
 (let =<< a (heredoc (list "trim") "EOS" (list "\thello" "world")))
 (let =<< a (heredoc (list) "EOS" (list)))
+(if v:true
+  ; matching leading indentation is accepted
+  (let =<< a (heredoc (list "trim") "EOS" (list "\t\thello" "\tworld")))
+  (let =<< a (heredoc (list "trim") "EOS" (list "   hello" "  world")))
+  ; but isn't required
+  (let =<< a (heredoc (list "trim") "EOS" (list "   hello" "  world"))))
+; we don't actually do the trimming for trim heredocs
+(let =<< a (heredoc (list "trim") "EOS" (list "  hello" "   world")))
+(let =<< a (heredoc (list "trim") "EOS" (list "\t  hello" "\t\tworld")))
diff --git a/test/test_heredoc.vim b/test/test_heredoc.vim
index e92322b..2bb06f9 100644
--- a/test/test_heredoc.vim
+++ b/test/test_heredoc.vim
@@ -8,3 +8,28 @@ world
 EOS
 let a =<< EOS
 EOS
+if v:true
+	" matching leading indentation is accepted
+	let a =<< trim EOS
+		hello
+	world
+	EOS
+  let a =<< trim EOS
+   hello
+  world
+  EOS
+	" but isn't required
+	let a =<< trim EOS
+   hello
+  world
+EOS
+endif
+" we don't actually do the trimming for trim heredocs
+let a =<< trim EOS
+  hello
+   world
+EOS
+  : let a =<< trim EOS
+	  hello
+		world
+EOS