diff --git a/Makefile b/Makefile
index b99fa6962..5ee5fb215 100644
--- a/Makefile
+++ b/Makefile
@@ -25,8 +25,8 @@ CPU_avx2		:= amd64
 TMPL_avx		:= fastint_amd64_test fastfloat_amd64_test native_amd64_test native_export_amd64
 TMPL_avx2		:= fastint_amd64_test fastfloat_amd64_test native_amd64_test native_export_amd64
 
-CFLAGS_avx		:= -msse4 -mavx -mno-avx2 -DUSE_AVX=1 -DUSE_AVX2=0 -DDEBUG=1
-CFLAGS_avx2		:= -msse4 -mavx -mavx2    -DUSE_AVX=1 -DUSE_AVX2=1 
+CFLAGS_avx		:= -msse4 -mavx -mno-avx2 -DUSE_AVX=1 -DUSE_AVX2=0
+CFLAGS_avx2		:= -msse4 -mavx -mavx2    -DUSE_AVX=1 -DUSE_AVX2=1
 
 CC_amd64		:= clang
 ASM2ASM_amd64	:= tools/asm2asm/asm2asm.py
diff --git a/api.go b/api.go
index 9456d81b0..88f8f9ed3 100644
--- a/api.go
+++ b/api.go
@@ -64,6 +64,9 @@ import (
     // CopyString indicates decoder to decode string values by copying instead of referring.
     CopyString                    bool
 
+    // ValidString indicates decoder to valid string values: decoder will return errors when
+    // invalid UTF-8 chars or unescaped control chars(\u0000-\u001f).
+    ValidString                    bool
  }
  
  var (
diff --git a/sonic.go b/sonic.go
index aebb9c917..7fa65598a 100644
--- a/sonic.go
+++ b/sonic.go
@@ -61,6 +61,8 @@ type frozenConfig struct {
 // Froze convert the Config to API
 func (cfg Config) Froze() API {
     api := &frozenConfig{Config: cfg}
+
+    // configure encoder options:
     if cfg.EscapeHTML {
         api.encoderOpts |= encoder.EscapeHTML
     }
@@ -73,6 +75,11 @@ func (cfg Config) Froze() API {
     if cfg.NoQuoteTextMarshaler {
         api.encoderOpts |= encoder.NoQuoteTextMarshaler
     }
+    if cfg.NoNullSliceOrMap {
+        api.encoderOpts |= encoder.NoNullSliceOrMap
+    }
+
+    // configure decoder options:
     if cfg.UseInt64 {
         api.decoderOpts |= decoder.OptionUseInt64
     }
@@ -85,8 +92,8 @@ func (cfg Config) Froze() API {
     if cfg.CopyString {
         api.decoderOpts |= decoder.OptionCopyString
     }
-    if cfg.NoNullSliceOrMap {
-        api.encoderOpts |= encoder.NoNullSliceOrMap
+    if cfg.ValidString {
+        api.decoderOpts |= decoder.OptionValidateString
     }
     return api
 }
@@ -111,7 +118,6 @@ func (cfg *frozenConfig) MarshalIndent(val interface{}, prefix, indent string) (
 func (cfg *frozenConfig) UnmarshalFromString(buf string, val interface{}) error {
     dec := decoder.NewDecoder(buf)
     dec.SetOptions(cfg.decoderOpts)
-    dec.ValidString()
     err := dec.Decode(val)
     pos := dec.Pos()