diff --git a/.circleci/config.yml b/.circleci/config.yml
index ca01db96480..43aaeb75e86 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -38,6 +38,7 @@ jobs:
             # Tests can take a long time to run, since we don't need to attach a debugger
             # a Debug build with with -O2 lets us avoid timeouts and get results sooner.
             cmake -S hermes -B build -GNinja -DHERMES_ENABLE_INTL=ON \
+              -DCMAKE_BUILD_TYPE=Debug \
               -DCMAKE_CXX_FLAGS=-O2 -DCMAKE_C_FLAGS=-O2 \
               -DHERMESVM_SANITIZE_HANDLES=<< parameters.sanitize >> \
               -DHERMES_ENABLE_UNDEFINED_BEHAVIOR_SANITIZER=<< parameters.sanitize >> \
@@ -67,6 +68,6 @@ jobs:
       - run:
           name: Run Hermes regression tests
           command: |
-            cmake -S hermes -B build
+            cmake -S hermes -B build -DCMAKE_BUILD_TYPE=Debug
             cmake --build build -j 2
             cmake --build build --target check-hermes -j 4
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index dc6c8676e0d..a7b1d07ef73 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -51,5 +51,5 @@ jobs:
         path: hermes
     - name: Run Hermes regression tests
       run: |-
-        cmake -S hermes -B build
+        cmake -S hermes -B build -DCMAKE_BUILD_TYPE=Debug
         cmake --build build --target check-hermes all -j 4
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d87b8dca9cf..607cb75b400 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -42,6 +42,11 @@ if (POLICY CMP0026)
   cmake_policy(SET CMP0026 OLD)
 endif()
 
+# Require a build type
+if ((NOT GENERATOR_IS_MULTI_CONFIG) AND (NOT DEFINED CMAKE_BUILD_TYPE OR CMAKE_BUILD_TYPE STREQUAL ""))
+    message(FATAL_ERROR "Please set CMAKE_BUILD_TYPE")
+endif()
+
 # Has to be set before `project` as per documentation
 # https://cmake.org/cmake/help/latest/variable/CMAKE_OSX_SYSROOT.html
 set(CMAKE_OSX_SYSROOT ${HERMES_APPLE_TARGET_PLATFORM})
@@ -337,11 +342,6 @@ if (HERMESVM_INTERNAL_JAVASCRIPT_NATIVE)
   add_definitions(-DHERMESVM_INTERNAL_JAVASCRIPT_NATIVE)
 endif()
 
-# Enable debug mode by default
-if ((NOT GENERATOR_IS_MULTI_CONFIG) AND CMAKE_BUILD_TYPE STREQUAL "")
-    set(CMAKE_BUILD_TYPE Debug)
-endif()
-
 if (HERMES_STATIC_LINK)
   append("-static" CMAKE_EXE_LINKER_FLAGS)
   set(HERMES_USE_STATIC_ICU ON)
diff --git a/README.md b/README.md
index cacdee5f386..e7ba177597c 100644
--- a/README.md
+++ b/README.md
@@ -23,7 +23,7 @@ To build a local debug version of the Hermes CLI tools the following steps shoul
 mkdir hermes_workingdir
 cd hermes_workingdir
 git clone https://github.com/facebook/hermes.git
-cmake -S hermes -B build -G Ninja
+cmake -S hermes -B build -G Ninja -DCMAKE_BUILD_TYPE=Debug
 cmake --build ./build
 ```
 
diff --git a/doc/BuildingAndRunning.md b/doc/BuildingAndRunning.md
index abfa1221f6b..045a9403aa0 100644
--- a/doc/BuildingAndRunning.md
+++ b/doc/BuildingAndRunning.md
@@ -33,7 +33,7 @@ Create a base directory to work in, e.g. `~/workspace`, and cd into it.
 After `cd`ing, follow the steps below to generate the Hermes build system:
 
     git clone https://github.com/facebook/hermes.git
-    cmake -S hermes -B build -G Ninja
+    cmake -S hermes -B build -G Ninja -DCMAKE_BUILD_TYPE=Debug
 
 The build system has now been generated in the `build` directory. To perform the build:
 
@@ -100,7 +100,7 @@ simply run:
  The `-HERMES_ENABLE_ADDRESS_SANITIZER=ON` flag will create a ASan build:
 
     git clone https://github.com/facebook/hermes.git
-    cmake -S hermes -B asan_build -G Ninja -D HERMES_ENABLE_ADDRESS_SANITIZER=ON
+    cmake -S hermes -B asan_build -G Ninja -D HERMES_ENABLE_ADDRESS_SANITIZER=ON -DCMAKE_BUILD_TYPE=Debug
     cmake --build ./asan_build
 
 You can verify the build by looking for `asan` symbols in the `hermes` binary: