diff --git a/compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs b/compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs
index 1a424c37050..8d847ca103b 100644
--- a/compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs
+++ b/compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs
@@ -725,6 +725,11 @@ impl<'brillig> Context<'brillig> {
 
         // Should we consider calls to slice_push_back and similar to be mutating operations as well?
         if let Store { value: array, .. } | ArraySet { array, .. } = instruction {
+            if function.dfg.is_global(*array) {
+                // Early return as we expect globals to be immutable.
+                return;
+            };
+
             let instruction = match &function.dfg[*array] {
                 Value::Instruction { instruction, .. } => &function.dfg[*instruction],
                 _ => return,