diff --git a/evm/src/cpu/kernel/assembler.rs b/evm/src/cpu/kernel/assembler.rs
index f52ae29d..0471bf99 100644
--- a/evm/src/cpu/kernel/assembler.rs
+++ b/evm/src/cpu/kernel/assembler.rs
@@ -563,13 +563,13 @@ mod tests {
         let kernel = parse_and_assemble(&["%stack (a, b, c) -> (b)"]);
         assert_eq!(kernel.code, vec![pop, swap1, pop]);
 
-        let kernel = parse_and_assemble(&["%stack (a, (b: 3), c) -> (c)"]);
+        let kernel = parse_and_assemble(&["%stack (a, b: 3, c) -> (c)"]);
         assert_eq!(kernel.code, vec![pop, pop, pop, pop]);
 
-        let kernel = parse_and_assemble(&["%stack ((a: 2), (b: 2)) -> (b, a)"]);
+        let kernel = parse_and_assemble(&["%stack (a: 2, b: 2) -> (b, a)"]);
         assert_eq!(kernel.code, vec![swap1, swap3, swap1, swap2]);
 
-        let kernel1 = parse_and_assemble(&["%stack ((a: 3), (b: 3), c) -> (c, b, a)"]);
+        let kernel1 = parse_and_assemble(&["%stack (a: 3, b: 3, c) -> (c, b, a)"]);
         let kernel2 =
             parse_and_assemble(&["%stack (a, b, c, d, e, f, g) -> (g, d, e, f, a, b, c)"]);
         assert_eq!(kernel1.code, kernel2.code);
diff --git a/evm/src/cpu/kernel/evm_asm.pest b/evm/src/cpu/kernel/evm_asm.pest
index 227e2466..89d06e74 100644
--- a/evm/src/cpu/kernel/evm_asm.pest
+++ b/evm/src/cpu/kernel/evm_asm.pest
@@ -23,8 +23,8 @@ paramlist = { "(" ~ identifier ~ ("," ~ identifier)* ~ ")" }
 macro_arglist = !{ "(" ~ push_target ~ ("," ~ push_target)* ~ ")" }
 stack = { ^"%stack" ~ stack_placeholders ~ "->" ~ stack_replacements }
 stack_placeholders = { "(" ~ stack_placeholder ~ ("," ~ stack_placeholder)* ~ ")" }
-stack_placeholder = { identifier | stack_block }
-stack_block = { "(" ~ identifier ~ ":" ~ literal_decimal ~ ")" }
+stack_placeholder = { stack_block | identifier }
+stack_block = { identifier ~ ":" ~ literal_decimal }
 stack_replacements = { "(" ~ stack_replacement ~ ("," ~ stack_replacement)* ~ ")" }
 stack_replacement = { literal | identifier | constant | macro_label | variable }
 global_label_decl = ${ ^"GLOBAL " ~ identifier ~ ":" }