diff --git a/schala-lang/language/src/symbol_table.rs b/schala-lang/language/src/symbol_table.rs
index 2ab5c69..0eb9a0e 100644
--- a/schala-lang/language/src/symbol_table.rs
+++ b/schala-lang/language/src/symbol_table.rs
@@ -7,7 +7,7 @@ use std::fmt::Write;
 use crate::schala::SourceMapHandle;
 use crate::source_map::{SourceMap, LineNumber};
 use crate::ast;
-use crate::ast::{ItemId, TypeBody, TypeSingletonName, Signature, Statement, StatementKind};
+use crate::ast::{ItemId, TypeBody, TypeSingletonName, Signature, Statement, StatementKind, ModuleSpecifier};
 use crate::typechecking::TypeName;
 
 
@@ -191,8 +191,6 @@ impl SymbolTable {
   fn add_symbols_from_scope<'a>(&'a mut self, statements: &Vec<Statement>, scope_name_stack: &mut Vec<ScopeSegment>) -> Result<(), String> {
     use self::ast::Declaration::*;
 
-          //Err(format!("Duplicate definition: {}. It's already defined at {}", name, line_number))
-
     let mut seen_identifiers = DuplicateNameTrackTable::new();
     let mut seen_modules = DuplicateNameTrackTable::new();
 
@@ -213,7 +211,7 @@ impl SymbolTable {
                 name: signature.name.clone(),
               });
               let output = self.add_symbols_from_scope(body, scope_name_stack);
-              let _ = scope_name_stack.pop();
+              scope_name_stack.pop();
               output?
             },
             TypeDecl { name, body, mutable } => {
@@ -229,8 +227,13 @@ impl SymbolTable {
             _ => ()
           }
         },
-        Statement { kind: StatementKind::Module(mod_spec), id } => {
-          ()
+        Statement { kind: StatementKind::Module(ModuleSpecifier { name, contents}), id } => {
+          seen_modules.try_register(&name, &id, &self.source_map_handle.borrow())
+            .map_err(|line| format!("Duplicate module definition: {}. It's already defined at {}", name, line))?;
+          scope_name_stack.push(ScopeSegment { name: name.clone() });
+          let output = self.add_symbols_from_scope(contents, scope_name_stack);
+          scope_name_stack.pop();
+          output?
         },
         _ => ()
       }
diff --git a/schala-lang/language/src/symbol_table/test.rs b/schala-lang/language/src/symbol_table/test.rs
index 96c147a..11c2d2d 100644
--- a/schala-lang/language/src/symbol_table/test.rs
+++ b/schala-lang/language/src/symbol_table/test.rs
@@ -156,16 +156,22 @@ inner_func(x)
 }
 
 #[test]
-fn modules() {
+fn duplicate_modules() {
   let source = r#"
-
-    module a {
+    module q {
+      fn foo() { 4 }
     }
 
     module a {
+      fn foo() { 334 }
+    }
 
+    module a {
+      fn foo() { 256.1 }
     }
     "#;
   let (_, output) = add_symbols_from_source(source);
-  //assert!(output.unwrap_err().contains("Duplicate"))
+  let output = output.unwrap_err();
+  assert!(output.contains("Duplicate module"));
+  assert!(output.contains("already defined at 5"));
 }