diff --git a/src/gates/gmimc.rs b/src/gates/gmimc.rs
index 63cf8918..dad8b078 100644
--- a/src/gates/gmimc.rs
+++ b/src/gates/gmimc.rs
@@ -149,7 +149,7 @@ impl<F: Field, const R: usize> Gate<F> for GMiMCGate<F, R> {
     }
 
     fn num_constraints(&self) -> usize {
-        R + W
+        R + W + 2
     }
 }
 
diff --git a/src/plonk_common.rs b/src/plonk_common.rs
index c1965995..1c2deb02 100644
--- a/src/plonk_common.rs
+++ b/src/plonk_common.rs
@@ -18,6 +18,8 @@ pub fn evaluate_gate_constraints<F: Field>(
     for gate in gates {
         let gate_constraints = gate.0.eval_filtered(vars);
         for (i, c) in gate_constraints.into_iter().enumerate() {
+            debug_assert!(i < num_gate_constraints,
+                          "num_constraints() gave too low of a number");
             constraints[i] += c;
         }
     }