diff --git a/cranelift/isle/isle/isle_examples/fail/multi_prio.isle b/cranelift/isle/isle/isle_examples/fail/multi_prio.isle
new file mode 100644
index 0000000000..30ce9c7a5f
--- /dev/null
+++ b/cranelift/isle/isle/isle_examples/fail/multi_prio.isle
@@ -0,0 +1,4 @@
+(type u32 (primitive u32))
+
+(decl multi A (u32) u32)
+(rule 0 (A x) x)
diff --git a/cranelift/isle/isle/isle_examples/link/multi_extractor.isle b/cranelift/isle/isle/isle_examples/link/multi_extractor.isle
index 5878dd0652..2630d86826 100644
--- a/cranelift/isle/isle/isle_examples/link/multi_extractor.isle
+++ b/cranelift/isle/isle/isle_examples/link/multi_extractor.isle
@@ -7,7 +7,7 @@
 
 (decl multi Rule (u32) u32)
 
-(rule 1 (Rule (E1 a idx))
+(rule (Rule (E1 a idx))
       (if-let (A.B) a)
       idx)
 (rule (Rule _)
diff --git a/cranelift/isle/isle/src/sema.rs b/cranelift/isle/isle/src/sema.rs
index 95481f1067..ba9906f853 100644
--- a/cranelift/isle/isle/src/sema.rs
+++ b/cranelift/isle/isle/src/sema.rs
@@ -1744,6 +1744,18 @@ impl TermEnv {
 
                     bindings.exit_scope();
 
+                    let prio = if let Some(prio) = rule.prio {
+                        if flags.multi {
+                            tyenv.report_error(
+                                pos,
+                                "Cannot set rule priorities in multi-terms".to_string(),
+                            );
+                        }
+                        prio
+                    } else {
+                        0
+                    };
+
                     let rid = RuleId(self.rules.len());
                     self.rules.push(Rule {
                         id: rid,
@@ -1752,7 +1764,7 @@ impl TermEnv {
                         iflets,
                         rhs,
                         vars: bindings.seen,
-                        prio: rule.prio.unwrap_or(0),
+                        prio,
                         pos,
                     });
                 }
diff --git a/cranelift/isle/isle/tests/run_tests.rs b/cranelift/isle/isle/tests/run_tests.rs
index 9adf51c32d..1b347b9454 100644
--- a/cranelift/isle/isle/tests/run_tests.rs
+++ b/cranelift/isle/isle/tests/run_tests.rs
@@ -15,8 +15,12 @@ pub fn run_pass(filename: &str) {
 }
 
 pub fn run_fail(filename: &str) {
-    if build(filename).is_ok() {
-        panic!("test {} passed unexpectedly", filename);
+    match build(filename) {
+        Ok(_) => panic!("test {} passed unexpectedly", filename),
+        Err(err) => {
+            // Log the actual errors for use with `cargo test -- --nocapture`
+            println!("failed, as expected:\n{:?}", err);
+        }
     }
 }