diff --git a/src/format.rs b/src/format.rs
index a2f1ffb..3285e06 100644
--- a/src/format.rs
+++ b/src/format.rs
@@ -85,7 +85,7 @@ pub trait Display {
   fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result;
 }
 
-pub fn format<T>(value: &T) -> Formatted<T> {
+pub fn format<'a, T>(value: &'a T) -> Formatted<'a, T> {
   Formatted(value)
 }
 
diff --git a/src/lib.rs b/src/lib.rs
index 4cb0d7f..5000e46 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1283,6 +1283,15 @@ mod tests {
   }
 
   #[rstest]
+  #[case(
+    "def definition() { \"foo\": \"bar\" } definition()",
+    "{ \"foo\": \"bar\" }"
+  )]
+  #[case(
+    "def letter() let message = \"foo\" { \"text\": $message } letter()",
+    "{ \"text\": \"foo\" }"
+  )]
+  #[case("def nuller() null nuller()", "null")]
   #[case("def my_add(a, b)\n $a + $b \n my_add(1, 2)", "3")]
   #[case("def my_add(a, b)\n let foo = $a \n $foo + $b \n my_add(1, 2)", "3")]
   #[case(
diff --git a/src/parser/jslt.pest b/src/parser/jslt.pest
index 6dc5afc..d79fb94 100644
--- a/src/parser/jslt.pest
+++ b/src/parser/jslt.pest
@@ -1,6 +1,6 @@
 Jslt = _{ SOI ~ Expr ~ EOI }
 
-Value = _{ Array | Object | Number | String | Boolean | Null | FunctionCall | Accessor | Scope | Variable }
+Value = _{ FunctionCall | Accessor | Scope | Variable | Array | Object | Number | String | Boolean | Null }
 
 Expr = _{ OperatorExpr | ValueExpr }
 ValueExpr = _{ VariableDef | FunctionDef | IfStatement | Value }
@@ -22,8 +22,8 @@ And = { "and" }
 Or = { "or" }
 If = _{ "if" }
 For = _{ "for" }
-Def = _{ "def" }
-Let = _{ "let" }
+Def = _{ "def " }
+Let = _{ "let " }
 
 Scope = { "(" ~ Expr ~ ")" }
 
@@ -35,8 +35,8 @@ FromRangeAccessor = { Expr ~ ":" ~ Expr? }
 ToRangeAccessor = { Expr? ~ ":" ~ Expr }
 RangeAccessor = { FromRangeAccessor | ToRangeAccessor }
 
-FunctionCall = { Ident ~ FunctionCallArgs ~ Accessor? }
-FunctionCallArgs = { "(" ~ Expr? ~ ("," ~ Expr)* ~ ")" }
+FunctionCall = ${ Ident ~ FunctionCallArgs ~ Accessor? }
+FunctionCallArgs = !{ "(" ~ Expr? ~ ("," ~ Expr)* ~ ")" }
 
 FunctionDef = { Def ~ Ident ~ "("  ~ Ident? ~ ("," ~ Ident)* ~ ")" ~ Expr ~ Expr? }