diff --git a/cmake/AwsTestHarness.cmake b/cmake/AwsTestHarness.cmake
index 84435b35ff..c146851068 100644
--- a/cmake/AwsTestHarness.cmake
+++ b/cmake/AwsTestHarness.cmake
@@ -39,6 +39,8 @@ function(generate_test_driver driver_exe_name)
     add_executable(${driver_exe_name} ${CMAKE_CURRENT_BINARY_DIR}/test_runner.c ${TESTS})
     aws_set_common_properties(${driver_exe_name} NO_WEXTRA NO_PEDANTIC)
 
+    set(CMAKE_BUILD_TYPE "DEBUG" CACHE STRING "Default build type: DEBUG" FORCE)
+
      # Some versions of CMake (3.9-3.11) generate a test_runner.c file with
      # a strncpy() call that triggers the "stringop-overflow" warning in GCC 8.1+
      # This warning doesn't exist until GCC 7 though, so test for it before disabling.