diff --git a/changelogs/unreleased/847-schaeff b/changelogs/unreleased/847-schaeff
new file mode 100644
index 00000000..d6d50a18
--- /dev/null
+++ b/changelogs/unreleased/847-schaeff
@@ -0,0 +1 @@
+Remove side effects on complex types (bug)
\ No newline at end of file
diff --git a/zokrates_core/src/static_analysis/mod.rs b/zokrates_core/src/static_analysis/mod.rs
index 4b91e49e..aaecb49c 100644
--- a/zokrates_core/src/static_analysis/mod.rs
+++ b/zokrates_core/src/static_analysis/mod.rs
@@ -9,7 +9,6 @@ mod constant_inliner;
 mod flat_propagation;
 mod flatten_complex_types;
 mod propagation;
-mod redefinition;
 mod reducer;
 mod shift_checker;
 mod uint_optimizer;
@@ -20,7 +19,6 @@ mod variable_write_remover;
 use self::bounds_checker::BoundsChecker;
 use self::flatten_complex_types::Flattener;
 use self::propagation::Propagator;
-use self::redefinition::RedefinitionOptimizer;
 use self::reducer::reduce_program;
 use self::shift_checker::ShiftChecker;
 use self::uint_optimizer::UintOptimizer;
@@ -84,8 +82,6 @@ impl<'ast, T: Field> TypedProgram<'ast, T> {
 
         // propagate
         let r = Propagator::propagate(r).map_err(Error::from)?;
-        // optimize redefinitions
-        let r = RedefinitionOptimizer::optimize(r);
         // remove assignment to variable index
         let r = VariableWriteRemover::apply(r);
         // remove variable access to complex types
diff --git a/zokrates_core/src/static_analysis/redefinition.rs b/zokrates_core/src/static_analysis/redefinition.rs
deleted file mode 100644
index f44a8450..00000000
--- a/zokrates_core/src/static_analysis/redefinition.rs
+++ /dev/null
@@ -1,73 +0,0 @@
-use crate::typed_absy::folder::*;
-use crate::typed_absy::*;
-use std::collections::HashMap;
-use zokrates_field::Field;
-
-pub struct RedefinitionOptimizer<'ast> {
-    identifiers: HashMap<Identifier<'ast>, Identifier<'ast>>,
-}
-
-impl<'ast> RedefinitionOptimizer<'ast> {
-    fn new() -> Self {
-        RedefinitionOptimizer {
-            identifiers: HashMap::new(),
-        }
-    }
-
-    pub fn optimize<T: Field>(p: TypedProgram<'ast, T>) -> TypedProgram<'ast, T> {
-        RedefinitionOptimizer::new().fold_program(p)
-    }
-}
-
-fn try_id<'ast, T: Field>(e: &TypedExpression<'ast, T>) -> Option<Identifier<'ast>> {
-    match e {
-        TypedExpression::FieldElement(FieldElementExpression::Identifier(id)) => Some(id.clone()),
-        TypedExpression::Boolean(BooleanExpression::Identifier(id)) => Some(id.clone()),
-        TypedExpression::Array(a) => match a.as_inner() {
-            ArrayExpressionInner::Identifier(id) => Some(id.clone()),
-            _ => None,
-        },
-        TypedExpression::Struct(a) => match a.as_inner() {
-            StructExpressionInner::Identifier(id) => Some(id.clone()),
-            _ => None,
-        },
-        TypedExpression::Uint(a) => match a.as_inner() {
-            UExpressionInner::Identifier(id) => Some(id.clone()),
-            _ => None,
-        },
-        _ => None,
-    }
-}
-
-impl<'ast, T: Field> Folder<'ast, T> for RedefinitionOptimizer<'ast> {
-    fn fold_function(&mut self, f: TypedFunction<'ast, T>) -> TypedFunction<'ast, T> {
-        self.identifiers = HashMap::new();
-        fold_function(self, f)
-    }
-
-    fn fold_statement(&mut self, s: TypedStatement<'ast, T>) -> Vec<TypedStatement<'ast, T>> {
-        match s {
-            TypedStatement::Definition(TypedAssignee::Identifier(var), expr) => {
-                let expr = self.fold_expression(expr);
-
-                match try_id(&expr) {
-                    Some(id) => {
-                        let target = self.identifiers.get(&id).unwrap_or(&id).clone();
-
-                        self.identifiers.insert(var.id, target);
-                        vec![]
-                    }
-                    None => vec![TypedStatement::Definition(
-                        TypedAssignee::Identifier(var),
-                        expr,
-                    )],
-                }
-            }
-            s => fold_statement(self, s),
-        }
-    }
-
-    fn fold_name(&mut self, s: Identifier<'ast>) -> Identifier<'ast> {
-        self.identifiers.get(&s).cloned().unwrap_or(s)
-    }
-}
diff --git a/zokrates_core_test/tests/tests/structs/identity.json b/zokrates_core_test/tests/tests/structs/identity.json
index 15db3e86..ac96fb97 100644
--- a/zokrates_core_test/tests/tests/structs/identity.json
+++ b/zokrates_core_test/tests/tests/structs/identity.json
@@ -1,5 +1,5 @@
 {
-	"entry_point": "./tests/tests/structs/identity.code",
+	"entry_point": "./tests/tests/structs/identity.zok",
 	"curves": ["Bn128", "Bls12_381", "Bls12_377", "Bw6_761"],
 	"tests": [
 		{
diff --git a/zokrates_core_test/tests/tests/structs/identity.code b/zokrates_core_test/tests/tests/structs/identity.zok
similarity index 100%
rename from zokrates_core_test/tests/tests/structs/identity.code
rename to zokrates_core_test/tests/tests/structs/identity.zok
diff --git a/zokrates_core_test/tests/tests/structs/if_else.zok b/zokrates_core_test/tests/tests/structs/if_else.zok
deleted file mode 100644
index e69de29b..00000000
diff --git a/zokrates_core_test/tests/tests/structs/mutate_argument.json b/zokrates_core_test/tests/tests/structs/mutate_argument.json
new file mode 100644
index 00000000..b307b14d
--- /dev/null
+++ b/zokrates_core_test/tests/tests/structs/mutate_argument.json
@@ -0,0 +1,16 @@
+{
+	"entry_point": "./tests/tests/structs/mutate_argument.zok",
+	"curves": ["Bn128", "Bls12_381", "Bls12_377", "Bw6_761"],
+	"tests": [
+		{
+			"input": {
+				"values": ["1"]
+			},
+			"output": {
+				"Ok": {
+					"values": ["2", "1"]
+				}
+			}
+		}
+	]
+}
diff --git a/zokrates_core_test/tests/tests/structs/mutate_argument.zok b/zokrates_core_test/tests/tests/structs/mutate_argument.zok
new file mode 100644
index 00000000..aa352fcd
--- /dev/null
+++ b/zokrates_core_test/tests/tests/structs/mutate_argument.zok
@@ -0,0 +1,10 @@
+struct Foo {
+    field a
+}
+
+def mutate(field[1] f) -> field[1]:
+    f[0] = f[0] + 1
+    return f
+
+def main(field[1] f) -> (field[1], field[1]):
+    return mutate(f), f
\ No newline at end of file