diff --git a/Cargo.toml b/Cargo.toml
index ff52d7b..744b795 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -75,3 +75,4 @@ cli = [
   "env_logger",
   "lazy_static",
 ]
+sign_ext = ["parity-wasm/sign_ext"]
diff --git a/src/gas/validation.rs b/src/gas/validation.rs
index 5bd2b2f..812c37d 100644
--- a/src/gas/validation.rs
+++ b/src/gas/validation.rs
@@ -25,7 +25,7 @@ type NodeId = usize;
 
 /// A node in a control flow graph is commonly known as a basic block. This is a sequence of
 /// operations that are always executed sequentially.
-#[derive(Debug)]
+#[derive(Debug, Default)]
 struct ControlFlowNode {
 	/// The index of the first instruction in the basic block. This is only used for debugging.
 	first_instr_pos: Option<usize>,
@@ -48,19 +48,6 @@ struct ControlFlowNode {
 	loopback_edges: Vec<NodeId>,
 }
 
-impl Default for ControlFlowNode {
-	fn default() -> Self {
-		ControlFlowNode {
-			first_instr_pos: None,
-			actual_cost: 0,
-			charged_cost: 0,
-			is_loop_target: false,
-			forward_edges: Vec::new(),
-			loopback_edges: Vec::new(),
-		}
-	}
-}
-
 /// A control flow graph where nodes are basic blocks and edges represent possible transitions
 /// between them in execution flow. The graph has two types of edges, forward and loop-back edges.
 /// The subgraph with only the forward edges forms a directed acyclic graph (DAG); including the
diff --git a/src/rules.rs b/src/rules.rs
index 6e33f95..4a1cbc3 100644
--- a/src/rules.rs
+++ b/src/rules.rs
@@ -65,6 +65,9 @@ pub enum InstructionType {
 	Nop,
 	CurrentMemory,
 	GrowMemory,
+
+	#[cfg(feature = "sign_ext")]
+	SignExt,
 }
 
 impl FromStr for InstructionType {
@@ -92,6 +95,10 @@ impl FromStr for InstructionType {
 			"nop" => Ok(InstructionType::Nop),
 			"current_mem" => Ok(InstructionType::CurrentMemory),
 			"grow_mem" => Ok(InstructionType::GrowMemory),
+
+			#[cfg(feature = "sign_ext")]
+			"sign_ext" => Ok(InstructionType::SignExt),
+
 			_ => Err(UnknownInstruction),
 		}
 	}
@@ -290,6 +297,9 @@ impl InstructionType {
 			I64ReinterpretF64 => InstructionType::Reinterpretation,
 			F32ReinterpretI32 => InstructionType::Reinterpretation,
 			F64ReinterpretI64 => InstructionType::Reinterpretation,
+
+			#[cfg(feature = "sign_ext")]
+			SignExt(_) => InstructionType::SignExt,
 		}
 	}
 }
diff --git a/src/stack_height/max_height.rs b/src/stack_height/max_height.rs
index 4e928d3..6b3d566 100644
--- a/src/stack_height/max_height.rs
+++ b/src/stack_height/max_height.rs
@@ -4,6 +4,9 @@ use super::{resolve_func_type, Error};
 use log::trace;
 use parity_wasm::elements::{self, BlockType, Type};
 
+#[cfg(feature = "sign_ext")]
+use parity_wasm::elements::SignExtInstruction;
+
 /// Control stack frame.
 #[derive(Debug)]
 struct Frame {
@@ -410,6 +413,16 @@ pub(crate) fn compute(func_idx: u32, module: &elements::Module) -> Result<u32, E
 				stack.pop_values(1)?;
 				stack.push_values(1)?;
 			},
+
+			#[cfg(feature = "sign_ext")]
+			SignExt(SignExtInstruction::I32Extend8S) |
+			SignExt(SignExtInstruction::I32Extend16S) |
+			SignExt(SignExtInstruction::I64Extend8S) |
+			SignExt(SignExtInstruction::I64Extend16S) |
+			SignExt(SignExtInstruction::I64Extend32S) => {
+				stack.pop_values(1)?;
+				stack.push_values(1)?;
+			},
 		}
 		pc += 1;
 	}