diff --git a/src/main/java/chocopy/pa2/TypeChecker.java b/src/main/java/chocopy/pa2/TypeChecker.java
index 6e18fa97c62d6dd77f97ecf7a5df00b80b5a8258..5703e38c55cbe9a08d2b86600f7042351c175556 100644
--- a/src/main/java/chocopy/pa2/TypeChecker.java
+++ b/src/main/java/chocopy/pa2/TypeChecker.java
@@ -328,8 +328,12 @@ public class TypeChecker extends AbstractNodeAnalyzer<SymbolType> {
 
     @Override
     public SymbolType analyze(IfExpr node) {
+        SymbolType condition_type = node.condition.dispatch(this);
         SymbolType then_type = node.thenExpr.dispatch(this);
         SymbolType else_type = node.elseExpr.dispatch(this);
+        if(!condition_type.equals(BOOL_TYPE)) {
+            err(node, "if_expr should have BOOL_TYPE");
+        }
         if(!then_type.equals(else_type)) {
             err(node, "then_type not equals to else_type. ");
         }