diff --git a/build/main.rs b/build/main.rs
index 8de1a6e..8bd8526 100644
--- a/build/main.rs
+++ b/build/main.rs
@@ -22,6 +22,7 @@ pub enum Error {
 	FailedToCopy(String),
 	Decoding(elements::Error, String),
 	Encoding(elements::Error),
+	Packing(utils::PackingError),
 	Optimizer,
 }
 
@@ -37,6 +38,12 @@ impl From<utils::OptimizerError> for Error {
 	}
 }
 
+impl From<utils::PackingError> for Error {
+	fn from(err: utils::PackingError) -> Self {
+		Error::Packing(err)
+	}
+}
+
 impl std::fmt::Display for Error {
 	fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
 		use Error::*;
@@ -46,6 +53,7 @@ impl std::fmt::Display for Error {
 			Decoding(ref err, ref file) => write!(f, "Decoding error ({}). Must be a valid wasm file {}. Pointed wrong file?", err, file),
 			Encoding(ref err) => write!(f, "Encoding error ({}). Almost impossible to happen, no free disk space?", err),
 			Optimizer => write!(f, "Optimization error due to missing export section. Pointed wrong file?"),
+			Packing(ref e) => write!(f, "Packing failed due to module structure error: {}. Sure used correct libraries for building contracts?", e),
 		}
 	}
 }
@@ -213,7 +221,8 @@ fn main() {
 			utils::optimize(&mut ctor_module, vec![CREATE_SYMBOL])
 				.unwrap_or_else(|e| die(Error::from(e)))
 		}
-		let ctor_module = utils::pack_instance(raw_module, ctor_module).expect("Packing failed");
+		let ctor_module = utils::pack_instance(raw_module, ctor_module)
+			.unwrap_or_else(|e| die(Error::from(e)));
 		parity_wasm::serialize_to_file(&path, ctor_module)
 			.unwrap_or_else(|e| die(Error::Encoding(e)))
 	} else {
diff --git a/src/lib.rs b/src/lib.rs
index 5e3aec5..8753ec7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -24,5 +24,5 @@ pub use optimizer::{optimize, Error as OptimizerError};
 pub use gas::inject_gas_counter;
 pub use logger::init_log;
 pub use ext::{externalize, externalize_mem, underscore_funcs, ununderscore_funcs, shrink_unknown_stack};
-pub use pack::pack_instance;
+pub use pack::{pack_instance, Error as PackingError};
 pub use runtime_type::inject_runtime_type;
diff --git a/src/pack.rs b/src/pack.rs
index 9fa66f8..1906dbd 100644
--- a/src/pack.rs
+++ b/src/pack.rs
@@ -1,3 +1,4 @@
+use std::fmt;
 use parity_wasm::elements::{
     self, Section, Opcode, DataSegment, InitExpr, Internal, External,
     ImportCountType,
@@ -19,10 +20,24 @@ pub enum Error {
     InvalidCreateSignature,
     NoCreateSymbol,
     InvalidCreateMember,
-    NoRetImported,
     NoImportSection,
 }
 
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        match *self {
+            Error::MalformedModule => write!(f, "Module internal references are inconsistent"),
+            Error::NoTypeSection => write!(f, "No type section in the module"),
+            Error::NoExportSection => write!(f, "No export section in the module"),
+            Error::NoCodeSection => write!(f, "No code section inthe module"),
+            Error::InvalidCreateSignature => write!(f, "Exported symbol `deploy` has invalid signature, should be () -> ()"),
+            Error::InvalidCreateMember => write!(f, "Exported symbol `deploy` should be a function"),
+            Error::NoCreateSymbol => write!(f, "No exported `deploy` symbol"),
+            Error::NoImportSection => write!(f, "No import section in the module"),
+        }
+    }
+}
+
 /// If module has an exported "_create" function we want to pack it into "constructor".
 /// `raw_module` is the actual contract code
 /// `ctor_module` is the constructor which should return `raw_module`