diff --git a/src/conditions/vrl.rs b/src/conditions/vrl.rs
index 3fb115e7ba7fc..5febe5ef1a222 100644
--- a/src/conditions/vrl.rs
+++ b/src/conditions/vrl.rs
@@ -63,6 +63,10 @@ impl ConditionalConfig for VrlConfig {
                 .to_string()
         })?;
 
+        if !program.final_type_info().result.is_boolean() {
+            return Err("VRL conditions must return a boolean.".into());
+        }
+
         if !warnings.is_empty() {
             let warnings = Formatter::new(&self.source, warnings).colored().to_string();
             warn!(message = "VRL compilation warning.", %warnings);
@@ -233,6 +237,12 @@ mod test {
                 Ok(()),
                 Ok(()),
             ),
+            (
+                log_event![],
+                r#""i_return_a_string""#,
+                Err("VRL conditions must return a boolean.".into()),
+                Ok(()),
+            ),
         ];
 
         for (event, source, build, check) in checks {