diff --git a/src/node_contextify.cc b/src/node_contextify.cc
index 456c273b2b6d9b..3a0d4d3a1fd642 100644
--- a/src/node_contextify.cc
+++ b/src/node_contextify.cc
@@ -411,7 +411,17 @@ class ContextifyContext {
     // false for vmResult.x = 5 where vmResult = vm.runInContext();
     bool is_contextual_store = ctx->global_proxy() != args.This();
 
-    if (!is_declared && args.ShouldThrowOnError() && is_contextual_store)
+    // Indicator to not return before setting (undeclared) function declarations
+    // on the sandbox in strict mode, i.e. args.ShouldThrowOnError() = true.
+    // True for 'function f() {}', 'this.f = function() {}',
+    // 'var f = function()'.
+    // In effect only for 'function f() {}' because
+    // var f = function(), is_declared = true
+    // this.f = function() {}, is_contextual_store = false.
+    bool is_function = value->IsFunction();
+
+    if (!is_declared && args.ShouldThrowOnError() && is_contextual_store &&
+    !is_function)
       return;
 
     ctx->sandbox()->Set(property, value);