diff --git a/src/main/java/chocopy/pa2/TypeChecker.java b/src/main/java/chocopy/pa2/TypeChecker.java
index 649990d..b5f1b0b 100644
--- a/src/main/java/chocopy/pa2/TypeChecker.java
+++ b/src/main/java/chocopy/pa2/TypeChecker.java
@@ -191,8 +191,10 @@ public class TypeChecker extends AbstractNodeAnalyzer<Type> {
                 for(int i = 0; i < lArgs; ++i){
                     Type p = fty.parameters.get(i);
                     Type c = types.get(i);
-                    if((p.isSpecialType()&&!p.equals(c)) || 
+                    if(((p.isSpecialType()&&!p.equals(c)) || 
                         (!p.isSpecialType()&&!StudentAnalysis.subClassOf(p, c, currentScope)))
+                        &&!(p.isListType()&&c.equals(Type.EMPTY_TYPE))
+                        )
                         err(node,"Expected type `%s`; got type `%s` in parameter %d", p, c, i);
                 }
             }
@@ -238,7 +240,7 @@ public class TypeChecker extends AbstractNodeAnalyzer<Type> {
     public Type analyze(IfExpr node) {
         Type condTy = node.condition.dispatch(this);
         if(!condTy.equals(Type.BOOL_TYPE)){
-            err(node, "If condition `%s` isn't a boolean expression.", node.condition);
+            err(node, "Condition expression cannot be of type `%s`", condTy.className());
         }
         
         Type ifTy = node.thenExpr.dispatch(this), 
@@ -252,7 +254,7 @@ public class TypeChecker extends AbstractNodeAnalyzer<Type> {
     public Type analyze(IfStmt node) {
         Type condTy = node.condition.dispatch(this);
         if(!condTy.equals(Type.BOOL_TYPE)){
-            err(node, "If condition `%s` isn't a boolean expression.", node.condition);
+            err(node, "Condition expression cannot be of type `%s`", condTy.className());
         }
         boolean prevReturned = returned, thenReturned;
         for(Stmt st : node.thenBody)
@@ -335,7 +337,8 @@ public class TypeChecker extends AbstractNodeAnalyzer<Type> {
                 Type thisArgTy = thisArg.setInferredType(thisArg.dispatch(this)), 
                      thisParamTy = funcTy.parameters.get(i + 1);
 
-                if(!thisParamTy.equals(thisArgTy) && !StudentAnalysis.subClassOf(thisParamTy, thisArgTy, currentScope))
+                if(!thisParamTy.equals(thisArgTy) && !StudentAnalysis.subClassOf(thisParamTy, thisArgTy, currentScope)
+                &&!(thisParamTy.isListType()&&thisArgTy.equals(Type.EMPTY_TYPE)))
                     err(node, "Expected type `%s`; got type `%s` in parameter %d", 
                             thisParamTy, thisArgTy, i + 1);
             }