diff --git a/native/jni/NativeFileList.mk b/native/jni/NativeFileList.mk
index 6ccfec911..f418f6ece 100644
--- a/native/jni/NativeFileList.mk
+++ b/native/jni/NativeFileList.mk
@@ -95,6 +95,7 @@ LATIN_IME_CORE_SRC_FILES := \
     $(addprefix utils/, \
         autocorrection_threshold_utils.cpp \
         char_utils.cpp \
+        jni_data_utils.cpp \
         log_utils.cpp \
         time_keeper.cpp)
 
diff --git a/native/jni/com_android_inputmethod_latin_BinaryDictionary.cpp b/native/jni/com_android_inputmethod_latin_BinaryDictionary.cpp
index 9098b714b..418c77d7c 100644
--- a/native/jni/com_android_inputmethod_latin_BinaryDictionary.cpp
+++ b/native/jni/com_android_inputmethod_latin_BinaryDictionary.cpp
@@ -302,7 +302,6 @@ static jint latinime_BinaryDictionary_getNextWord(JNIEnv *env, jclass clazz,
     int wordCodePoints[outCodePointsLength];
     memset(wordCodePoints, 0, sizeof(wordCodePoints));
     const int nextToken = dictionary->getNextWordAndNextToken(token, wordCodePoints);
-    env->SetIntArrayRegion(outCodePoints, 0, outCodePointsLength, wordCodePoints);
     JniDataUtils::outputCodePoints(env, outCodePoints, 0 /* start */,
             MAX_WORD_LENGTH /* maxLength */, wordCodePoints, outCodePointsLength,
             false /* needsNullTermination */);
diff --git a/native/jni/src/utils/jni_data_utils.cpp b/native/jni/src/utils/jni_data_utils.cpp
new file mode 100644
index 000000000..5555293d5
--- /dev/null
+++ b/native/jni/src/utils/jni_data_utils.cpp
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "utils/jni_data_utils.h"
+
+namespace latinime {
+
+const int JniDataUtils::CODE_POINT_REPLACEMENT_CHARACTER = 0xFFFD;
+const int JniDataUtils::CODE_POINT_NULL = 0;
+
+} // namespace latinime
diff --git a/native/jni/src/utils/jni_data_utils.h b/native/jni/src/utils/jni_data_utils.h
index 0e393e315..01a5685b4 100644
--- a/native/jni/src/utils/jni_data_utils.h
+++ b/native/jni/src/utils/jni_data_utils.h
@@ -23,6 +23,7 @@
 #include "jni.h"
 #include "suggest/core/policy/dictionary_header_structure_policy.h"
 #include "suggest/policyimpl/dictionary/header/header_read_write_utils.h"
+#include "utils/char_utils.h"
 
 namespace latinime {
 
@@ -69,16 +70,31 @@ class JniDataUtils {
             const int maxLength, const int *const codePoints, const int codePointCount,
             const bool needsNullTermination) {
         const int outputCodePointCount = std::min(maxLength, codePointCount);
-        env->SetIntArrayRegion(intArrayToOutputCodePoints, start, outputCodePointCount, codePoints);
+        int outputCodePonts[outputCodePointCount];
+        for (int i = 0; i < outputCodePointCount; ++i) {
+            const int codePoint = codePoints[i];
+            if (!CharUtils::isInUnicodeSpace(codePoint)) {
+                outputCodePonts[i] = CODE_POINT_REPLACEMENT_CHARACTER;
+            } else if (codePoint >= 0x01 && codePoint <= 0x1F) {
+                // Control code.
+                outputCodePonts[i] = CODE_POINT_REPLACEMENT_CHARACTER;
+            } else {
+                outputCodePonts[i] = codePoint;
+            }
+        }
+        env->SetIntArrayRegion(intArrayToOutputCodePoints, start, outputCodePointCount,
+                outputCodePonts);
         if (needsNullTermination && outputCodePointCount < maxLength) {
-            const int terminal = 0;
             env->SetIntArrayRegion(intArrayToOutputCodePoints, start + outputCodePointCount,
-                    1 /* len */, &terminal);
+                    1 /* len */, &CODE_POINT_NULL);
         }
     }
 
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(JniDataUtils);
+
+    static const int CODE_POINT_REPLACEMENT_CHARACTER;
+    static const int CODE_POINT_NULL;
 };
 } // namespace latinime
 #endif // LATINIME_JNI_DATA_UTILS_H