3 files changed, 42 insertions, 3 deletions
diff --git a/src/jvm/clojure/lang/AFn.java b/src/jvm/clojure/lang/AFn.java
index a93cd7ed..26d2a56f 100644
--- a/src/jvm/clojure/lang/AFn.java
+++ b/src/jvm/clojure/lang/AFn.java
@@ -436,7 +436,6 @@ static public Object applyToHelper(IFn ifn, ISeq arglist) throws Exception{
 public Object throwArity(int n){
 	String name = getClass().getSimpleName();
 	int suffix = name.lastIndexOf("__");
-	throw new IllegalArgumentException("Wrong number of args (" + n + ") passed to: "
-	                                   + (suffix == -1 ? name : name.substring(0, suffix)).replace('_', '-'));
+	throw new ArityException(n, (suffix == -1 ? name : name.substring(0, suffix)).replace('_', '-'));
 }
 }
diff --git a/src/jvm/clojure/lang/ArityException.java b/src/jvm/clojure/lang/ArityException.java
new file mode 100644
index 00000000..71041ee3
--- /dev/null
+++ b/src/jvm/clojure/lang/ArityException.java
@@ -0,0 +1,32 @@
+/**
+ *   Copyright (c) Rich Hickey. All rights reserved.
+ *   The use and distribution terms for this software are covered by the
+ *   Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
+ *   which can be found in the file epl-v10.html at the root of this distribution.
+ *   By using this software in any fashion, you are agreeing to be bound by
+ * 	 the terms of this license.
+ *   You must not remove this notice, or any other, from this software.
+ **/
+
+package clojure.lang;
+
+/**
+ * @since 1.3
+ */
+public class ArityException extends IllegalArgumentException {
+
+	final public int actual;
+
+	final public String name;
+
+	public ArityException(int actual, String name) {
+		this(actual, name, null);
+	}
+
+	public ArityException(int actual, String name, Throwable cause) {
+		super("Wrong number of args (" + actual + ") passed to: " + name, cause);
+		this.actual = actual;
+		this.name = name;
+	}
+
+}
diff --git a/src/jvm/clojure/lang/Compiler.java b/src/jvm/clojure/lang/Compiler.java
index d38d25e8..34d46783 100644
--- a/src/jvm/clojure/lang/Compiler.java
+++ b/src/jvm/clojure/lang/Compiler.java
@@ -6027,7 +6027,15 @@ public static Object macroexpand1(Object x) throws Exception{
 		Var v = isMacro(op);
 		if(v != null)
 			{
-			return v.applyTo(RT.cons(form,RT.cons(LOCAL_ENV.get(),form.next())));
+				try
+					{
+						return v.applyTo(RT.cons(form,RT.cons(LOCAL_ENV.get(),form.next())));
+					}
+				catch(ArityException e)
+					{
+						// hide the 2 extra params for a macro
+						throw new ArityException(e.actual - 2, e.name, e);
+					}
 			}
 		else
 			{