diff --git a/compiler/noirc_evaluator/src/ssa/opt/flatten_cfg/value_merger.rs b/compiler/noirc_evaluator/src/ssa/opt/flatten_cfg/value_merger.rs
index 0a351148fa3..b7a76cf2b93 100644
--- a/compiler/noirc_evaluator/src/ssa/opt/flatten_cfg/value_merger.rs
+++ b/compiler/noirc_evaluator/src/ssa/opt/flatten_cfg/value_merger.rs
@@ -72,6 +72,11 @@ impl<'a> ValueMerger<'a> {
             "Expected values merged to be of the same type but found {then_type} and {else_type}"
         );
 
+        // Don't merge two values if they're already equal. That can make them non-constant
+        if then_value == else_value {
+            return then_value;
+        }
+
         let then_call_stack = self.dfg.get_value_call_stack(then_value);
         let else_call_stack = self.dfg.get_value_call_stack(else_value);