diff --git a/include/rapidjson/prettywriter.h b/include/rapidjson/prettywriter.h
index 14b8477..fff8886 100644
--- a/include/rapidjson/prettywriter.h
+++ b/include/rapidjson/prettywriter.h
@@ -100,8 +100,9 @@ public:
             Base::os_->Put('\n');
             WriteIndent();
         }
-        if (!Base::WriteEndObject())
-            return false;
+        bool ret = Base::WriteEndObject();
+        (void)ret;
+        RAPIDJSON_ASSERT(ret == true);
         if (Base::level_stack_.Empty()) // end of json text
             Base::os_->Flush();
         return true;
@@ -123,8 +124,9 @@ public:
             Base::os_->Put('\n');
             WriteIndent();
         }
-        if (!Base::WriteEndArray())
-            return false;
+        bool ret = Base::WriteEndArray();
+        (void)ret;
+        RAPIDJSON_ASSERT(ret == true);
         if (Base::level_stack_.Empty()) // end of json text
             Base::os_->Flush();
         return true;
diff --git a/include/rapidjson/writer.h b/include/rapidjson/writer.h
index bf17f3a..40cdb35 100644
--- a/include/rapidjson/writer.h
+++ b/include/rapidjson/writer.h
@@ -272,7 +272,8 @@ protected:
                     os_->Put(hexDigits[(codepoint >>  4) & 15]);
                     os_->Put(hexDigits[(codepoint      ) & 15]);
                 }
-                else if (codepoint >= 0x010000 && codepoint <= 0x10FFFF)    {
+                else {
+                    RAPIDJSON_ASSERT(codepoint >= 0x010000 && codepoint <= 0x10FFFF);
                     // Surrogate pair
                     unsigned s = codepoint - 0x010000;
                     unsigned lead = (s >> 10) + 0xD800;
@@ -288,8 +289,6 @@ protected:
                     os_->Put(hexDigits[(trail >>  4) & 15]);
                     os_->Put(hexDigits[(trail      ) & 15]);                    
                 }
-                else
-                    return false;   // invalid code point
             }
             else if ((sizeof(Ch) == 1 || (unsigned)c < 256) && escape[(unsigned char)c])  {
                 is.Take();
diff --git a/test/unittest/prettywritertest.cpp b/test/unittest/prettywritertest.cpp
index fcb1121..3b2355f 100644
--- a/test/unittest/prettywritertest.cpp
+++ b/test/unittest/prettywritertest.cpp
@@ -80,6 +80,15 @@ TEST(PrettyWriter, SetIndent) {
         buffer.GetString());
 }
 
+TEST(PrettyWriter, String) {
+    StringBuffer buffer;
+    PrettyWriter<StringBuffer> writer(buffer);
+    EXPECT_TRUE(writer.StartArray());
+    EXPECT_TRUE(writer.String("Hello\n"));
+    EXPECT_TRUE(writer.EndArray());
+    EXPECT_STREQ("[\n    \"Hello\\n\"\n]", buffer.GetString());
+}
+
 #if RAPIDJSON_HAS_STDSTRING
 TEST(PrettyWriter, String_STDSTRING) {
     StringBuffer buffer;
diff --git a/test/unittest/writertest.cpp b/test/unittest/writertest.cpp
index 7b9fa9a..d8193ca 100644
--- a/test/unittest/writertest.cpp
+++ b/test/unittest/writertest.cpp
@@ -343,4 +343,33 @@ TEST(Writer, InvalidEncoding) {
         static const UTF32<>::Ch s[] = { 0x110000, 0 }; // Out of U+0000 to U+10FFFF
         EXPECT_FALSE(writer.String(s));
     }
-}
\ No newline at end of file
+}
+
+TEST(Writer, InvalidEventSequence) {
+    // {]
+    {
+        StringBuffer buffer;
+        Writer<StringBuffer> writer(buffer);
+        writer.StartObject();
+        EXPECT_THROW(writer.EndArray(), AssertException);
+        EXPECT_FALSE(writer.IsComplete());
+    }
+
+    // [}
+    {
+        StringBuffer buffer;
+        Writer<StringBuffer> writer(buffer);
+        writer.StartArray();
+        EXPECT_THROW(writer.EndObject(), AssertException);
+        EXPECT_FALSE(writer.IsComplete());
+    }
+
+    // { 1: 
+    {
+        StringBuffer buffer;
+        Writer<StringBuffer> writer(buffer);
+        writer.StartObject();
+        EXPECT_THROW(writer.Int(1), AssertException);
+        EXPECT_FALSE(writer.IsComplete());
+    }
+}