diff --git a/libchisel/src/checkstartfunc.rs b/libchisel/src/checkstartfunc.rs
index 004af69..30b1062 100644
--- a/libchisel/src/checkstartfunc.rs
+++ b/libchisel/src/checkstartfunc.rs
@@ -1,4 +1,4 @@
-use super::ModuleValidator;
+use super::{ModuleError, ModuleValidator};
 use parity_wasm::elements::Module;
 
 /// Struct on which ModuleValidator is implemented.
@@ -15,7 +15,7 @@ impl CheckStartFunc {
 }
 
 impl ModuleValidator for CheckStartFunc {
-    fn validate(&self, module: &Module) -> Result<bool, String> {
+    fn validate(&self, module: &Module) -> Result<bool, ModuleError> {
         Ok(module.start_section().is_some() == self.start_required)
     }
 }
diff --git a/libchisel/src/deployer.rs b/libchisel/src/deployer.rs
index b9e995e..f3082b5 100644
--- a/libchisel/src/deployer.rs
+++ b/libchisel/src/deployer.rs
@@ -1,4 +1,4 @@
-use super::ModuleCreator;
+use super::{ModuleCreator, ModuleError};
 use parity_wasm::builder;
 use parity_wasm::elements::{CustomSection, Module};
 
@@ -148,7 +148,7 @@ fn create_memory_deployer(payload: &[u8]) -> Module {
 }
 
 impl<'a> ModuleCreator for Deployer<'a> {
-    fn create(&self) -> Result<Module, String> {
+    fn create(&self) -> Result<Module, ModuleError> {
         let output = match self {
             Deployer::Memory(payload) => create_memory_deployer(&payload),
             Deployer::CustomSection(payload) => create_custom_deployer(&payload),
diff --git a/libchisel/src/lib.rs b/libchisel/src/lib.rs
index 0f42969..5b65eb9 100644
--- a/libchisel/src/lib.rs
+++ b/libchisel/src/lib.rs
@@ -11,22 +11,28 @@ pub mod trimexports;
 pub mod verifyexports;
 pub mod verifyimports;
 
+#[derive(Eq, PartialEq, Debug)]
+pub enum ModuleError {
+    NotSupported,
+    Custom(String),
+}
+
 pub trait ModuleCreator {
     /// Returns new module.
-    fn create(&self) -> Result<Module, String>;
+    fn create(&self) -> Result<Module, ModuleError>;
 }
 
 pub trait ModuleTranslator {
-    /// Translates module. Returns new module.
-    fn translate(&self, module: &Module) -> Result<Module, String>;
+    /// Translates module. Returns new module. Can fail with ModuleError::NotSupported.
+    fn translate(&self, module: &Module) -> Result<Module, ModuleError>;
 
-    /// Translates module in-place. Returns true if the module was modified.
-    fn translate_inplace(&self, module: &mut Module) -> Result<bool, String>;
+    /// Translates module in-place. Returns true if the module was modified. Can fail with ModuleError::NotSupported.
+    fn translate_inplace(&self, module: &mut Module) -> Result<bool, ModuleError>;
 }
 
 pub trait ModuleValidator {
     /// Validates module. Returns true if it is valid or false if invalid.
-    fn validate(&self, module: &Module) -> Result<bool, String>;
+    fn validate(&self, module: &Module) -> Result<bool, ModuleError>;
 }
 
 #[cfg(test)]
@@ -36,22 +42,22 @@ mod tests {
     struct SampleModule {}
 
     impl ModuleCreator for SampleModule {
-        fn create(&self) -> Result<Module, String> {
+        fn create(&self) -> Result<Module, ModuleError> {
             Ok(Module::default())
         }
     }
 
     impl ModuleTranslator for SampleModule {
-        fn translate(&self, module: &Module) -> Result<Module, String> {
+        fn translate(&self, module: &Module) -> Result<Module, ModuleError> {
             Ok(Module::default())
         }
-        fn translate_inplace(&self, module: &mut Module) -> Result<bool, String> {
+        fn translate_inplace(&self, module: &mut Module) -> Result<bool, ModuleError> {
             Ok((true))
         }
     }
 
     impl ModuleValidator for SampleModule {
-        fn validate(&self, module: &Module) -> Result<bool, String> {
+        fn validate(&self, module: &Module) -> Result<bool, ModuleError> {
             Ok(true)
         }
     }
diff --git a/libchisel/src/remapimports.rs b/libchisel/src/remapimports.rs
index 4629a69..a61a54b 100644
--- a/libchisel/src/remapimports.rs
+++ b/libchisel/src/remapimports.rs
@@ -1,6 +1,6 @@
 use std::collections::HashMap;
 
-use super::ModuleTranslator;
+use super::{ModuleError, ModuleTranslator};
 use parity_wasm::elements::*;
 
 #[derive(Hash, Eq, PartialEq, Debug, Clone)]
@@ -204,11 +204,11 @@ impl RemapImports {
 }
 
 impl ModuleTranslator for RemapImports {
-    fn translate_inplace(&self, module: &mut Module) -> Result<bool, String> {
+    fn translate_inplace(&self, module: &mut Module) -> Result<bool, ModuleError> {
         Ok(rename_imports(module, &self.translations))
     }
 
-    fn translate(&self, module: &Module) -> Result<Module, String> {
+    fn translate(&self, module: &Module) -> Result<Module, ModuleError> {
         let mut ret = module.clone();
         rename_imports(&mut ret, &self.translations);
         Ok(ret)
diff --git a/libchisel/src/trimexports.rs b/libchisel/src/trimexports.rs
index 50a9a1f..94dfb3e 100644
--- a/libchisel/src/trimexports.rs
+++ b/libchisel/src/trimexports.rs
@@ -1,4 +1,4 @@
-use super::ModuleTranslator;
+use super::{ModuleError, ModuleTranslator};
 use parity_wasm::elements::*;
 
 /// Struct containing a list of valid exports.
@@ -102,11 +102,11 @@ impl TrimExports {
 }
 
 impl ModuleTranslator for TrimExports {
-    fn translate_inplace(&self, module: &mut Module) -> Result<bool, String> {
+    fn translate_inplace(&self, module: &mut Module) -> Result<bool, ModuleError> {
         Ok(self.trim_exports(module))
     }
 
-    fn translate(&self, module: &Module) -> Result<Module, String> {
+    fn translate(&self, module: &Module) -> Result<Module, ModuleError> {
         let mut ret = module.clone();
         self.trim_exports(&mut ret);
         Ok(ret)
diff --git a/libchisel/src/verifyexports.rs b/libchisel/src/verifyexports.rs
index c17713a..d7275ef 100644
--- a/libchisel/src/verifyexports.rs
+++ b/libchisel/src/verifyexports.rs
@@ -1,4 +1,4 @@
-use super::ModuleValidator;
+use super::{ModuleError, ModuleValidator};
 use parity_wasm::elements::{
     ExportSection, External, FunctionSection, FunctionType, ImportSection, Internal, Module, Type,
 };
@@ -38,7 +38,7 @@ impl<'a> VerifyExports<'a> {
 }
 
 impl<'a> ModuleValidator for VerifyExports<'a> {
-    fn validate(&self, module: &Module) -> Result<bool, String> {
+    fn validate(&self, module: &Module) -> Result<bool, ModuleError> {
         // FIXME: This validating algorithm runs in O(n^2). Needs to be optimized
         let required_exports_not_found = self
             .entries
diff --git a/libchisel/src/verifyimports.rs b/libchisel/src/verifyimports.rs
index 653cdee..08f8d32 100644
--- a/libchisel/src/verifyimports.rs
+++ b/libchisel/src/verifyimports.rs
@@ -1,4 +1,4 @@
-use super::ModuleValidator;
+use super::{ModuleError, ModuleValidator};
 use parity_wasm::elements::{External, FunctionType, ImportSection, Module, Type, ValueType};
 
 /// Enum representing a type of import and any extra data to check.
@@ -295,7 +295,7 @@ impl<'a> VerifyImports<'a> {
 }
 
 impl<'a> ModuleValidator for VerifyImports<'a> {
-    fn validate(&self, module: &Module) -> Result<bool, String> {
+    fn validate(&self, module: &Module) -> Result<bool, ModuleError> {
         let import_section_len = if let Some(section) = module.import_section() {
             section.entries().len()
         } else {