diff --git a/src/main/java/me/topchetoeu/jscript/compilation/CompoundNode.java b/src/main/java/me/topchetoeu/jscript/compilation/CompoundNode.java
index 958b825..9d8bd93 100644
--- a/src/main/java/me/topchetoeu/jscript/compilation/CompoundNode.java
+++ b/src/main/java/me/topchetoeu/jscript/compilation/CompoundNode.java
@@ -13,7 +13,7 @@ import me.topchetoeu.jscript.common.parsing.Source;
 
 public class CompoundNode extends Node {
     public final Node[] statements;
-    public final boolean hasScope;
+    public boolean hasScope;
     public Location end;
 
     @Override public void resolve(CompileResult target) {
diff --git a/src/main/java/me/topchetoeu/jscript/compilation/FunctionNode.java b/src/main/java/me/topchetoeu/jscript/compilation/FunctionNode.java
index f0ade70..9c369b8 100644
--- a/src/main/java/me/topchetoeu/jscript/compilation/FunctionNode.java
+++ b/src/main/java/me/topchetoeu/jscript/compilation/FunctionNode.java
@@ -107,6 +107,7 @@ public abstract class FunctionNode extends Node {
         this.end = end;
         this.params = params;
         this.body = body;
+        this.body.hasScope = false;
     }
 
     public static void compileWithName(Node stm, CompileResult target, boolean pollute, String name) {
diff --git a/src/main/java/me/topchetoeu/jscript/compilation/scope/FunctionScope.java b/src/main/java/me/topchetoeu/jscript/compilation/scope/FunctionScope.java
index e935be3..5daf8aa 100644
--- a/src/main/java/me/topchetoeu/jscript/compilation/scope/FunctionScope.java
+++ b/src/main/java/me/topchetoeu/jscript/compilation/scope/FunctionScope.java
@@ -19,6 +19,13 @@ public class FunctionScope extends Scope {
 
     public final boolean passtrough;
 
+    @Override public boolean hasNonStrict(String name) {
+        if (functionVarMap.containsKey(name)) return true;
+        if (blacklistNames.contains(name)) return true;
+
+        return false;
+    }
+
     @Override public Variable define(Variable var, Location loc) {
         checkNotEnded();
         if (strictVarMap.containsKey(var.name)) throw alreadyDefinedErr(loc, var.name);
@@ -32,13 +39,6 @@ public class FunctionScope extends Scope {
             return variables.add(var);
         }
     }
-    @Override public Variable defineStrict(Variable var, Location loc) {
-        checkNotEnded();
-        if (functionVarMap.containsKey(var.name)) throw alreadyDefinedErr(loc, var.name);
-        if (blacklistNames.contains(var.name)) throw alreadyDefinedErr(loc, var.name);
-
-        return super.defineStrict(var, loc);
-    }
     public Variable defineSpecial(Variable var, Location loc) {
         checkNotEnded();
         if (strictVarMap.containsKey(var.name)) throw alreadyDefinedErr(loc, var.name);
diff --git a/src/main/java/me/topchetoeu/jscript/compilation/scope/Scope.java b/src/main/java/me/topchetoeu/jscript/compilation/scope/Scope.java
index 206e990..3e210f7 100644
--- a/src/main/java/me/topchetoeu/jscript/compilation/scope/Scope.java
+++ b/src/main/java/me/topchetoeu/jscript/compilation/scope/Scope.java
@@ -86,6 +86,11 @@ public class Scope {
         return null;
     }
 
+    /**
+     * Checks if this scope's function parent has a non-strict variable of the given name
+     */
+    public boolean hasNonStrict(String name) { return false; }
+
     /**
      * Defines an ES2015-style variable
      * @param readonly True if const, false if let
@@ -96,6 +101,7 @@ public class Scope {
     public Variable defineStrict(Variable var, Location loc) {
         checkNotEnded();
         if (strictVarMap.containsKey(var.name)) throw alreadyDefinedErr(loc, var.name);
+        if (hasNonStrict(var.name)) throw alreadyDefinedErr(loc, var.name);
 
         strictVarMap.put(var.name, var);
         return variables.add(var);