diff --git a/.travis.yml b/.travis.yml
index 09da1592..b14ac263 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -36,7 +36,7 @@ install:
   - export TOKENIZER_ROOT=$HOME/Tokenizer
   - export SENTENCEPIECE_ROOT=$HOME/sentencepiece-$SENTENCEPIECE_VERSION
   - mkdir build && cd build
-  - cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=$TOKENIZER_ROOT -DCMAKE_PREFIX_PATH=$SENTENCEPIECE_ROOT -DWITH_ICU=$WITH_ICU ..
+  - cmake -DCMAKE_INSTALL_PREFIX=$TOKENIZER_ROOT -DCMAKE_PREFIX_PATH=$SENTENCEPIECE_ROOT -DWITH_ICU=$WITH_ICU ..
   - make install
   - cd $ROOT_TRAVIS_DIR
 script:
diff --git a/CMakeLists.txt b/CMakeLists.txt
index f6997985..496ab2ad 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -13,6 +13,10 @@ option(BUILD_SHARED_LIBS "Build shared libraries" ON)
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 
+if(NOT CMAKE_BUILD_TYPE)
+  set(CMAKE_BUILD_TYPE Release)
+endif(NOT CMAKE_BUILD_TYPE)
+
 if(MSVC)
   if(NOT BUILD_SHARED_LIBS)
     if(CMAKE_VERSION VERSION_LESS "3.15.0")
diff --git a/README.md b/README.md
index ca4f3139..5752e2db 100644
--- a/README.md
+++ b/README.md
@@ -80,7 +80,7 @@ See the `-h` flag to list the available options.
 ```
 mkdir build
 cd build
-cmake -DCMAKE_BUILD_TYPE=<Release or Debug> ..
+cmake ..
 make
 ```
 
diff --git a/bindings/python/tools/build_wheel.sh b/bindings/python/tools/build_wheel.sh
index 87b19924..26182347 100644
--- a/bindings/python/tools/build_wheel.sh
+++ b/bindings/python/tools/build_wheel.sh
@@ -35,7 +35,7 @@ cd $ROOT_DIR
 # Build Tokenizer.
 mkdir build
 cd build
-cmake -DCMAKE_BUILD_TYPE=Release -DLIB_ONLY=ON -DWITH_ICU=ON ..
+cmake -DLIB_ONLY=ON -DWITH_ICU=ON ..
 make -j2 install
 cd $ROOT_DIR