diff --git a/ergotree-interpreter/src/eval.rs b/ergotree-interpreter/src/eval.rs
index 77e09833b..8535163a7 100644
--- a/ergotree-interpreter/src/eval.rs
+++ b/ergotree-interpreter/src/eval.rs
@@ -3,6 +3,7 @@ use ergotree_ir::mir::constant::TryExtractInto;
 use ergotree_ir::pretty_printer::PosTrackingWriter;
 use ergotree_ir::pretty_printer::Print;
 use ergotree_ir::sigma_protocol::sigma_boolean::SigmaProp;
+use std::fmt::Display;
 use std::rc::Rc;
 
 use ergotree_ir::mir::expr::Expr;
@@ -106,6 +107,15 @@ pub struct ReductionDiagnosticInfo {
     pub pretty_printed_expr: Option<String>,
 }
 
+impl Display for ReductionDiagnosticInfo {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        if let Some(expr_str) = &self.pretty_printed_expr {
+            writeln!(f, "Pretty printed expr:\n{}", expr_str)?;
+        }
+        write!(f, "Env:\n{}", self.env)
+    }
+}
+
 /// Result of expression reduction procedure (see `reduce_to_crypto`).
 #[derive(PartialEq, Eq, Debug, Clone)]
 pub struct ReductionResult {
diff --git a/ergotree-interpreter/src/sigma_protocol/prover.rs b/ergotree-interpreter/src/sigma_protocol/prover.rs
index c4a0267c1..4dee08edc 100644
--- a/ergotree-interpreter/src/sigma_protocol/prover.rs
+++ b/ergotree-interpreter/src/sigma_protocol/prover.rs
@@ -79,7 +79,7 @@ pub enum ProverError {
     #[error("Script reduced to false")]
     ReducedToFalse,
     /// Script reduced to false with diagnostic info
-    #[error("Script reduced to false. Diagnostic info: {0:?}")]
+    #[error("Script reduced to false. Diagnostic info: {0}")]
     ReducedToFalseWithDiag(ReductionDiagnosticInfo),
     /// Failed on step2(prover does not have enough witnesses to perform the proof)
     #[error("Failed on step2(prover does not have enough witnesses to perform the proof)")]