diff --git a/server/src/content/template.rs b/server/src/content/template.rs
index 9e248b60a..1efb8620a 100644
--- a/server/src/content/template.rs
+++ b/server/src/content/template.rs
@@ -430,6 +430,7 @@ impl TriangleDef {
             ));
         }
 
+        let role_set: std::collections::BTreeSet<&RoleId> = self.roles.iter().collect();
         for (i, constraint) in self.relationship_constraints.iter().enumerate() {
             if constraint.required_trust.min > constraint.required_trust.max {
                 return Err(format!(
@@ -437,6 +438,12 @@ impl TriangleDef {
                     i, constraint.required_trust.min, constraint.required_trust.max
                 ));
             }
+            if !role_set.contains(&constraint.with_role) {
+                return Err(format!(
+                    "relationship_constraints[{}]: with_role '{}' not in triangle roles",
+                    i, constraint.with_role.0
+                ));
+            }
         }
 
         Ok(())