diff --git a/src/analysis.cpp b/src/analysis.cpp
index a367361..25fba58 100644
--- a/src/analysis.cpp
+++ b/src/analysis.cpp
@@ -214,6 +214,9 @@ AnalysisResult analyze(Node &ast, Memory &memory) {
                     throw TypeError(ErrorType::AlreadyDeclaredIdentifier, token.pos, identifier);
 
                 Type type = try_string_to_type(type_string, type_token.pos);
+                if (type.type == TypeType::Void)
+                    throw TypeError(ErrorType::IncompleteType, token.pos, {});
+
                 memory.declare(identifier, type);
                 
                 return {};
@@ -229,6 +232,9 @@ AnalysisResult analyze(Node &ast, Memory &memory) {
                     throw TypeError(ErrorType::AlreadyDeclaredIdentifier, token.pos, identifier);
 
                 Type type = try_string_to_type(type_string, type_token.pos);
+                if (type.type == TypeType::Void)
+                    throw TypeError(ErrorType::IncompleteType, token.pos, {});
+
                 memory.declare(identifier, type);
 
                 get_cast(type, analyze(node.children[2], memory), get_node_pos(node));
@@ -295,6 +301,15 @@ AnalysisResult analyze(Node &ast, Memory &memory) {
                     }
                 }
 
+                for (int i=1; i < (int)prototype.size(); i++) {
+                    if (get<0>(prototype.at(i)).type == TypeType::Void) {
+                        InnerNode args_node = get<InnerNode>(node.children[2]);
+                        InnerNode declaration_node = get<InnerNode>(args_node.children[i-1]);
+                        CodePosition type_pos = get_node_pos(declaration_node.children[0]);
+                        throw TypeError(ErrorType::IncompleteType, type_pos, {});
+                    }
+                }
+
                 memory.declare(function_name, type);
 
                 return {};
@@ -335,6 +350,15 @@ AnalysisResult analyze(Node &ast, Memory &memory) {
                     }
                 }
 
+                for (int i=1; i < (int)prototype.size(); i++) {
+                    if (get<0>(prototype.at(i)).type == TypeType::Void) {
+                        InnerNode args_node = get<InnerNode>(node.children[2]);
+                        InnerNode declaration_node = get<InnerNode>(args_node.children[i-1]);
+                        CodePosition type_pos = get_node_pos(declaration_node.children[0]);
+                        throw TypeError(ErrorType::IncompleteType, type_pos, {});
+                    }
+                }
+
                 memory.declare(function_name, type);
 
                 memory.update(function_name, node.children[3]);
diff --git a/src/errors.cpp b/src/errors.cpp
index ca5fc82..1a991fa 100644
--- a/src/errors.cpp
+++ b/src/errors.cpp
@@ -46,6 +46,7 @@ string UserError::get_message(void) const {
         case ErrorType::IncompatibleDefinition: return "Declaration of '"+get<string>(this->data)+"' is incompatible with previous prototype";
         case ErrorType::UnexpectedArgumentCount: return "Expected "+to_string(get<int>(this->data))+" arguments to function call";
         case ErrorType::IncompatibleReturnValue: return "Return value type does not match the function type";
+        case ErrorType::IncompleteType: return "Incomplete type is not allowed";
         
         // Runtime
         case ErrorType::UnknownIdentifier: return "Unknown identifier '"+get<string>(this->data)+"'";
diff --git a/src/include/errors.h b/src/include/errors.h
index 4e27a0c..4f9f2ae 100644
--- a/src/include/errors.h
+++ b/src/include/errors.h
@@ -45,6 +45,7 @@ enum class ErrorType {
     IncompatibleDefinition, // function declaration incompatible with prototype
     UnexpectedArgumentCount,
     IncompatibleReturnValue,
+    IncompleteType, // void x
 
     // Runtime
     UnknownIdentifier,
diff --git a/test/functions.cpp b/test/functions.cpp
index 5c42735..567af3f 100644
--- a/test/functions.cpp
+++ b/test/functions.cpp
@@ -98,5 +98,17 @@ int main() {
         true
     );
 
+    _TEST_ASSERT(
+        _TEST_IS_EXCEPTION(execute("int f(int x, void y);"), ErrorType::IncompleteType),
+        "Argument void (prototype)",
+        true
+    );
+
+    _TEST_ASSERT(
+        _TEST_IS_EXCEPTION(execute("int f(int x, void y) { return x+2; };"), ErrorType::IncompleteType),
+        "Argument void (déclaration)",
+        true
+    );
+
     return 0;
 }
\ No newline at end of file
diff --git a/test/variables.cpp b/test/variables.cpp
index b55ccdc..6938560 100644
--- a/test/variables.cpp
+++ b/test/variables.cpp
@@ -35,6 +35,12 @@ int main() {
         true
     );
 
+    _TEST_ASSERT(
+        _TEST_IS_EXCEPTION(execute("void x;"), ErrorType::IncompleteType),
+        "Type void",
+        true
+    );
+
     _TEST_ASSERT(
         _TEST_NO_EXCEPTION(holds_alternative<monostate>(execute("int x; { int x; }"))),
         "Identifieur déjà défini dans une autre scope",