diff --git a/src/error.rs b/src/error.rs
index bc6510b1f129f..72eedba5e3e18 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -116,7 +116,7 @@ impl<'tcx> Error for EvalError<'tcx> {
             EvalError::AssumptionNotHeld =>
                 "`assume` argument was false",
             EvalError::InlineAsm =>
-                "cannot evaluate inline assembly",
+                "miri does not support inline assembly",
             EvalError::TypeNotPrimitive(_) =>
                 "expected primitive type, got nonprimitive",
             EvalError::ReallocatedStaticMemory =>
diff --git a/src/eval_context.rs b/src/eval_context.rs
index 31c4915185da1..2a2a5829d3777 100644
--- a/src/eval_context.rs
+++ b/src/eval_context.rs
@@ -1437,6 +1437,12 @@ pub fn eval_main<'a, 'tcx: 'a>(
     let mut ecx = EvalContext::new(tcx, limits);
     let mir = ecx.load_mir(def_id).expect("main function's MIR not found");
 
+    if !mir.return_ty.is_nil() || mir.arg_count != 0 {
+        let msg = "miri does not support main functions without `fn()` type signatures";
+        tcx.sess.err(&EvalError::Unimplemented(String::from(msg)).to_string());
+        return;
+    }
+
     ecx.push_stack_frame(
         def_id,
         DUMMY_SP,