diff --git src/jvm/clojure/lang/Compiler.java src/jvm/clojure/lang/Compiler.java
index 352bfd8..5725d78 100644
--- src/jvm/clojure/lang/Compiler.java
+++ src/jvm/clojure/lang/Compiler.java
@@ -6479,6 +6479,7 @@ public static Object eval(Object form, boolean freshLoader) {
 		Var.pushThreadBindings(RT.map(LINE, line));
 		try
 			{
+			checkLet(form); // Fix CLJ-5
 			form = macroexpand(form);
 			if(form instanceof IPersistentCollection && Util.equals(RT.first(form), DO))
 				{
@@ -6522,6 +6523,42 @@ public static Object eval(Object form, boolean freshLoader) {
 		}
 }
 
+private static void checkLet(Object x) {
+  if (x instanceof ISeq)
+    {
+      ISeq form = (ISeq) x;
+      Object op = RT.first(form);
+      if (op instanceof clojure.lang.Symbol)
+        {
+          Symbol symbol = (Symbol)op;
+          if (symbol.getName().equals("let"))
+            {
+              Object arg = RT.second(form);
+              if (arg instanceof clojure.lang.PersistentVector)
+                {
+                  PersistentVector v = (PersistentVector)arg;
+                  for (int i = 0; i < v.size(); i = i+2)
+                    {
+                      Object leftSide = v.get(i);
+                      if (!(leftSide instanceof clojure.lang.Symbol))
+                        {
+                          throw new UnsupportedOperationException("left side " +
+                              "of binding to let() must be a symbol (found a " +
+                              leftSide.getClass().getSimpleName() + " instead).");
+                        }
+                    }
+                }
+              else
+                {
+                  throw new UnsupportedOperationException("argument to (let) " +
+                      " must be a vector (found a " +
+                      arg.getClass().getSimpleName() +" instead).");
+                }
+            }
+        }
+    }
+  }
+
 private static int registerConstant(Object o){
 	if(!CONSTANTS.isBound())
 		return -1;