diff --git a/zokrates_core_test/tests/tests/fact_up_to_4.zok b/zokrates_core_test/tests/tests/fact_up_to_4.zok
index 299cd995..7ca60112 100644
--- a/zokrates_core_test/tests/tests/fact_up_to_4.zok
+++ b/zokrates_core_test/tests/tests/fact_up_to_4.zok
@@ -1,8 +1,8 @@
 import "utils/casts/u32_to_field" as to_field
 
 def main(field x) -> field:
-    field f = 1
-    field counter = 0
+    field mut f = 1
+    field mut counter = 0
     for u32 i in 1..5 do
         f = if counter == x then f else f * to_field(i) fi
         counter = if counter == x then counter else counter + 1 fi
diff --git a/zokrates_core_test/tests/tests/memoize/no_array_memoization.zok b/zokrates_core_test/tests/tests/memoize/no_array_memoization.zok
index e3a60bac..15898f2a 100644
--- a/zokrates_core_test/tests/tests/memoize/no_array_memoization.zok
+++ b/zokrates_core_test/tests/tests/memoize/no_array_memoization.zok
@@ -2,7 +2,7 @@ def foo(field[1] a) -> field:
 	return a[0]
 
 def main():
-	field[1] a = [1]
+	field[1] mut a = [1]
 	field b = foo(a)
 	a[0] = 0
 	field c = foo(a)
diff --git a/zokrates_core_test/tests/tests/native_le.zok b/zokrates_core_test/tests/tests/native_le.zok
index 95ec21f4..1d9aea53 100644
--- a/zokrates_core_test/tests/tests/native_le.zok
+++ b/zokrates_core_test/tests/tests/native_le.zok
@@ -5,9 +5,9 @@ from "field" import FIELD_MAX, FIELD_SIZE_IN_BITS
 // this comparison works for any N smaller than the field size, which is the case in practice
 def le<N>(bool[N] a_bits, bool[N] c_bits) -> bool:
 
-    bool size_unknown = false
+    bool mut size_unknown = false
 
-    u32 verified_conditions = 0 // `and(conditions) == (sum(conditions) == len(conditions))`, here we initialize `sum(conditions)`
+    u32 mut verified_conditions = 0 // `and(conditions) == (sum(conditions) == len(conditions))`, here we initialize `sum(conditions)`
 
     size_unknown = true
 
diff --git a/zokrates_core_test/tests/tests/nested_loop.zok b/zokrates_core_test/tests/tests/nested_loop.zok
index 00ee862f..213b9b15 100644
--- a/zokrates_core_test/tests/tests/nested_loop.zok
+++ b/zokrates_core_test/tests/tests/nested_loop.zok
@@ -1,8 +1,8 @@
 def main(field[4] values) -> (field, field, field):
-    field res0 = 1
-    field res1 = 0
+    field mut res0 = 1
+    field mut res1 = 0
 
-    u32 counter = 0
+    u32 mut counter = 0
 
     for u32 i in 0..4 do
         for u32 j in i..4 do
@@ -15,9 +15,9 @@ def main(field[4] values) -> (field, field, field):
         res1 = res1 + 1
     endfor
 
-    field res2 = 0
-    u32 i = 0
-    for u32 i in i..5 do
+    field mut res2 = 0
+    u32 mut i = 0
+    for u32 mut i in i..5 do
         i = 5
         for u32 i in 0..i do
             res2 = res2 + 1
diff --git a/zokrates_core_test/tests/tests/pass_by_value.zok b/zokrates_core_test/tests/tests/pass_by_value.zok
index 66ca524f..a5e35e63 100644
--- a/zokrates_core_test/tests/tests/pass_by_value.zok
+++ b/zokrates_core_test/tests/tests/pass_by_value.zok
@@ -2,15 +2,15 @@ struct Foo {
     field a
 }
 
-def mutate(field a) -> field:
+def mutate(field mut a) -> field:
     a = a + 1
     return a
 
-def mutate(Foo f) -> Foo:
+def mutate(Foo mut f) -> Foo:
     f.a = f.a + 1
     return f
 
-def mutate(field[1] f) -> field[1]:
+def mutate(field[1] mut f) -> field[1]:
     f[0] = f[0] + 1
     return f
 
diff --git a/zokrates_core_test/tests/tests/structs/constant.zok b/zokrates_core_test/tests/tests/structs/constant.zok
index 15d3db40..58a8909c 100644
--- a/zokrates_core_test/tests/tests/structs/constant.zok
+++ b/zokrates_core_test/tests/tests/structs/constant.zok
@@ -3,6 +3,6 @@ struct State {
 }
 
 def main():
-	State s = State { memory: [0; 16] }
+	State mut s = State { memory: [0; 16] }
 	s.memory[0] = 0x00000001
 	return
\ No newline at end of file
diff --git a/zokrates_core_test/tests/tests/tuples/constant.zok b/zokrates_core_test/tests/tests/tuples/constant.zok
index 2a2b0703..737fddb5 100644
--- a/zokrates_core_test/tests/tests/tuples/constant.zok
+++ b/zokrates_core_test/tests/tests/tuples/constant.zok
@@ -1,4 +1,4 @@
 def main():
-	(u32[16],) s = ([0; 16],)
+	(u32[16],) mut s = ([0; 16],)
 	s.0[0] = 0x00000001
 	return
\ No newline at end of file
diff --git a/zokrates_core_test/tests/tests/uint/add_loop.zok b/zokrates_core_test/tests/tests/uint/add_loop.zok
index cb416240..4af52b12 100644
--- a/zokrates_core_test/tests/tests/uint/add_loop.zok
+++ b/zokrates_core_test/tests/tests/uint/add_loop.zok
@@ -1,6 +1,6 @@
 // 32 constraints for input constraining
 def main(u32 a) -> u32:
-	u32 res = 0x00000000
+	u32 mut res = 0x00000000
 	for u32 i in 0..10 do
 		res = res + a
 	endfor
diff --git a/zokrates_core_test/tests/tests/uint/sha256.zok b/zokrates_core_test/tests/tests/uint/sha256.zok
index 1c8022c4..fc7056e7 100644
--- a/zokrates_core_test/tests/tests/uint/sha256.zok
+++ b/zokrates_core_test/tests/tests/uint/sha256.zok
@@ -28,14 +28,14 @@ def temp2(u32 a, u32 b, u32 c) -> u32:
 
 def main(u32[1][16] input) -> u32[8]:	
 
-	u32 h0 = 0x6a09e667
-	u32 h1 = 0xbb67ae85
-	u32 h2 = 0x3c6ef372
-	u32 h3 = 0xa54ff53a
-	u32 h4 = 0x510e527f
-	u32 h5 = 0x9b05688c
-	u32 h6 = 0x1f83d9ab
-	u32 h7 = 0x5be0cd19
+	u32 mut h0 = 0x6a09e667
+	u32 mut h1 = 0xbb67ae85
+	u32 mut h2 = 0x3c6ef372
+	u32 mut h3 = 0xa54ff53a
+	u32 mut h4 = 0x510e527f
+	u32 mut h5 = 0x9b05688c
+	u32 mut h6 = 0x1f83d9ab
+	u32 mut h7 = 0x5be0cd19
 
 	u32[64] k = [0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da, 0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070, 0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2]
 
@@ -44,21 +44,21 @@ def main(u32[1][16] input) -> u32[8]:
 
 	for u32 i in 0..1 do
 
-		u32[64] w = [...input[0], ...[0x00000000; 48]]
+		u32[64] mut w = [...input[0], ...[0x00000000; 48]]
 
 		for u32 i in 16..64 do
 	        u32 r = extend(w, i)
 	        w[i] = r
 		endfor
 
-		u32 a = h0
-		u32 b = h1
-		u32 c = h2
-		u32 d = h3
-		u32 e = h4
-		u32 f = h5
-		u32 g = h6
-		u32 h = h7
+		u32 mut a = h0
+		u32 mut b = h1
+		u32 mut c = h2
+		u32 mut d = h3
+		u32 mut e = h4
+		u32 mut f = h5
+		u32 mut g = h6
+		u32 mut h = h7
 
 		for u32 i in 0..64 do