diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -24,6 +24,10 @@
 include(AddCompilerFlags)
 remove_compiler_flags(-DNDEBUG)
 
+# Define the debugging symbols DEBUG and DEBUG_LOCKORDER when the Debug build
+# type is selected.
+string(APPEND CMAKE_CXX_FLAGS_DEBUG " -DDEBUG -DDEBUG_LOCKORDER")
+
 # Ensure that WINDRES_PREPROC is enabled when using windres.
 if(${CMAKE_SYSTEM_NAME} MATCHES "Windows")
 	list(APPEND CMAKE_RC_FLAGS "-DWINDRES_PREPROC")