diff --git a/tooling/ast_fuzzer/src/compare/compiled.rs b/tooling/ast_fuzzer/src/compare/compiled.rs
index 88639cad13a..7f81f3e8bf4 100644
--- a/tooling/ast_fuzzer/src/compare/compiled.rs
+++ b/tooling/ast_fuzzer/src/compare/compiled.rs
@@ -232,7 +232,11 @@ impl Comparable for InputValue {
 
 impl std::fmt::Display for NargoErrorWithTypes {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        std::fmt::Display::fmt(&self.0, f)
+        if let Some(msg) = self.user_defined_failure_message() {
+            write!(f, "{}: {}", self.0, msg)
+        } else {
+            std::fmt::Display::fmt(&self.0, f)
+        }
     }
 }
 
diff --git a/tooling/ast_fuzzer/src/compare/interpreted.rs b/tooling/ast_fuzzer/src/compare/interpreted.rs
index 114f1088fe4..0e62964ffaa 100644
--- a/tooling/ast_fuzzer/src/compare/interpreted.rs
+++ b/tooling/ast_fuzzer/src/compare/interpreted.rs
@@ -175,7 +175,11 @@ impl Comparable for ssa::interpreter::errors::InterpreterError {
                 BinaryOp::Add { unchecked: false } => msg == "attempt to add with overflow",
                 BinaryOp::Sub { unchecked: false } => msg == "attempt to subtract with overflow",
                 BinaryOp::Mul { unchecked: false } => msg == "attempt to multiply with overflow",
-                BinaryOp::Shl | BinaryOp::Shr => msg == "attempt to bit-shift with overflow",
+                BinaryOp::Shl | BinaryOp::Shr => {
+                    msg == "attempt to bit-shift with overflow"
+                        || msg == "attempt to shift right with overflow"
+                        || msg == "attempt to shift left with overflow"
+                }
                 _ => false,
             },
             (
diff --git a/tooling/ast_fuzzer/src/compare/mod.rs b/tooling/ast_fuzzer/src/compare/mod.rs
index 9465b25e1e0..89f64245f41 100644
--- a/tooling/ast_fuzzer/src/compare/mod.rs
+++ b/tooling/ast_fuzzer/src/compare/mod.rs
@@ -136,11 +136,11 @@ where
             }
             CompareResult::LeftFailed(e, _) => {
                 let e = &e.error;
-                bail!("first program failed: {e}\n{e:?}")
+                bail!("first program failed: {e}\n\n{e:?}")
             }
             CompareResult::RightFailed(_, e) => {
                 let e = &e.error;
-                bail!("second program failed: {e}\n{e:?}")
+                bail!("second program failed: {e}\n\n{e:?}")
             }
             CompareResult::BothPassed(o1, o2) => match (&o1.return_value, &o2.return_value) {
                 (Some(r1), Some(r2)) if !Comparable::equivalent(r1, r2) => {
diff --git a/tooling/ast_fuzzer/src/lib.rs b/tooling/ast_fuzzer/src/lib.rs
index fa23f242b21..1166864a6e6 100644
--- a/tooling/ast_fuzzer/src/lib.rs
+++ b/tooling/ast_fuzzer/src/lib.rs
@@ -103,7 +103,7 @@ impl Default for Config {
             ("assign", 30),
             ("if", 10),
             ("match", 10),
-            ("for", 25),
+            ("for", 30),
             ("let", 25),
             ("call", 5),
             ("constrain", 4),
@@ -120,7 +120,7 @@ impl Default for Config {
             ("let", 20),
             ("call", 5),
             ("print", 15),
-            ("constrain", 10),
+            ("constrain", 15),
         ]);
         Self {
             max_globals: 3,