diff --git a/Cargo.toml b/Cargo.toml
index 4f5cdeb..f41f559 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "spartan"
-version = "0.2.0"
+version = "0.2.1"
 authors = ["Srinath Setty <srinath@microsoft.com>"]
 edition = "2018"
 description = "High-speed zkSNARKs without trusted setup"
diff --git a/src/errors.rs b/src/errors.rs
index 8b04c9a..4917979 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -14,6 +14,7 @@ impl fmt::Debug for ProofVerifyError {
   }
 }
 
+#[derive(Clone, Debug, Eq, PartialEq)]
 pub enum R1CSError {
   /// returned if the number of constraints is not a power of 2
   NonPowerOfTwoCons,
@@ -25,16 +26,6 @@ pub enum R1CSError {
   InvalidNumberOfVars,
   /// returned if a [u8;32] does not parse into a valid Scalar in the field of ristretto255
   InvalidScalar,
-}
-
-impl fmt::Display for R1CSError {
-  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-    write!(f, "R1CSError")
-  }
-}
-
-impl fmt::Debug for R1CSError {
-  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-    write!(f, "{{ file: {}, line: {} }}", file!(), line!())
-  }
+  /// returned if the supplied row or col in (row,col,val) tuple is out of range
+  InvalidIndex,
 }
diff --git a/src/lib.rs b/src/lib.rs
index a090d38..be781d3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -129,6 +129,17 @@ impl Instance {
         let mut mat: Vec<(usize, usize, Scalar)> = Vec::new();
         for i in 0..tups.len() {
           let (row, col, val_bytes) = tups[i];
+
+          // row must be smaller than num_cons
+          if row >= num_cons {
+            return Err(R1CSError::InvalidIndex);
+          }
+
+          // col must be smaller than num_vars + 1 + num_inputs
+          if col >= num_vars + 1 + num_inputs {
+            return Err(R1CSError::InvalidIndex);
+          }
+
           let val = Scalar::from_bytes(&val_bytes);
           if val.is_some().unwrap_u8() == 1 {
             mat.push((row, col, val.unwrap()));
@@ -140,12 +151,18 @@ impl Instance {
       };
 
     let A_scalar = bytes_to_scalar(A);
+    if A_scalar.is_err() {
+      return Err(A_scalar.err().unwrap());
+    }
+
     let B_scalar = bytes_to_scalar(B);
-    let C_scalar = bytes_to_scalar(C);
+    if B_scalar.is_err() {
+      return Err(B_scalar.err().unwrap());
+    }
 
-    // check for any parsing errors
-    if A_scalar.is_err() || B_scalar.is_err() || C_scalar.is_err() {
-      return Err(R1CSError::InvalidScalar);
+    let C_scalar = bytes_to_scalar(C);
+    if C_scalar.is_err() {
+      return Err(C_scalar.err().unwrap());
     }
 
     let inst = R1CSInstance::new(
@@ -161,16 +178,19 @@ impl Instance {
   }
 
   /// Checks if a given R1CSInstance is satisfiable with a given variables and inputs assignments
-  pub fn is_sat(&self, vars: &VarsAssignment, inputs: &InputsAssignment) -> Result<bool, R1CSError> {
-    
+  pub fn is_sat(
+    &self,
+    vars: &VarsAssignment,
+    inputs: &InputsAssignment,
+  ) -> Result<bool, R1CSError> {
     if vars.assignment.len() != self.inst.get_num_vars() {
-      return Err(R1CSError::InvalidNumberOfVars)
+      return Err(R1CSError::InvalidNumberOfVars);
     }
-    
+
     if inputs.assignment.len() != self.inst.get_num_inputs() {
-      return Err(R1CSError::InvalidNumberOfInputs)
+      return Err(R1CSError::InvalidNumberOfInputs);
     }
- 
+
     Ok(self.inst.is_sat(&vars.assignment, &inputs.assignment))
   }
 
@@ -485,4 +505,49 @@ mod tests {
       .verify(&comm, &inputs, &mut verifier_transcript, &gens)
       .is_ok());
   }
+
+  #[test]
+  pub fn check_r1cs_invalid_index() {
+    let num_cons = 4;
+    let num_vars = 8;
+    let num_inputs = 1;
+
+    let zero: [u8; 32] = [
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0,
+    ];
+
+    let A = vec![(0, 0, zero)];
+    let B = vec![(100, 1, zero)];
+    let C = vec![(1, 1, zero)];
+
+    let inst = Instance::new(num_cons, num_vars, num_inputs, &A, &B, &C);
+    assert_eq!(inst.is_err(), true);
+    assert_eq!(inst.err(), Some(R1CSError::InvalidIndex));
+  }
+
+  #[test]
+  pub fn check_r1cs_invalid_scalar() {
+    let num_cons = 4;
+    let num_vars = 8;
+    let num_inputs = 1;
+
+    let zero: [u8; 32] = [
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+      0,
+    ];
+
+    let larger_than_mod = [
+      3, 0, 0, 0, 255, 255, 255, 255, 254, 91, 254, 255, 2, 164, 189, 83, 5, 216, 161, 9, 8, 216,
+      57, 51, 72, 125, 157, 41, 83, 167, 237, 115,
+    ];
+
+    let A = vec![(0, 0, zero)];
+    let B = vec![(1, 1, larger_than_mod)];
+    let C = vec![(1, 1, zero)];
+
+    let inst = Instance::new(num_cons, num_vars, num_inputs, &A, &B, &C);
+    assert_eq!(inst.is_err(), true);
+    assert_eq!(inst.err(), Some(R1CSError::InvalidScalar));
+  }
 }