diff --git a/lib/lexer.js b/lib/lexer.js
index c5d2b467..0ea85e64 100644
--- a/lib/lexer.js
+++ b/lib/lexer.js
@@ -431,7 +431,7 @@
               if (before.length) {
                 tokens.push(['STRING', quote + before + quote]);
               }
-              nested = lexer.tokenize(expression.substring(2, expression.length - 1), {
+              nested = lexer.tokenize('(' + expression.substring(2, expression.length - 1) + ')', {
                 rewrite: false
               });
               nested.pop();
diff --git a/src/lexer.coffee b/src/lexer.coffee
index c86da8cb..ff6cc449 100644
--- a/src/lexer.coffee
+++ b/src/lexer.coffee
@@ -367,7 +367,7 @@ exports.Lexer: class Lexer
             tokens.push ['STRING', quote + before.substring(0, before.length - 1) + expression + quote] if before.length
           else
             tokens.push ['STRING', quote + before + quote] if before.length
-            nested: lexer.tokenize expression.substring(2, expression.length - 1), {rewrite: no}
+            nested: lexer.tokenize '(' + expression.substring(2, expression.length - 1) + ')', {rewrite: no}
             nested.pop()
             tokens.push ['TOKENS', nested]
           str: str.substring(group.length)
diff --git a/test/test_string_interpolation.coffee b/test/test_string_interpolation.coffee
index 87152447..dd3fecad 100644
--- a/test/test_string_interpolation.coffee
+++ b/test/test_string_interpolation.coffee
@@ -8,6 +8,7 @@ ok "[$hello$world]" is '[HelloWorld]'
 ok "[${hello}${world}]" is '[HelloWorld]'
 ok "$hello$$world" is 'Hello$World'
 ok "${hello}$${world}" is 'Hello$World'
+ok "Hello ${ 1 + 2 } World" is 'Hello 3 World'
 
 [s, t, r, i, n, g]: ['s', 't', 'r', 'i', 'n', 'g']
 ok "$s$t$r$i$n$g" is 'string'