diff --git a/CHANGES b/CHANGES
index 3ba2089357..e260100247 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,12 @@
+6.0.0-dev.617 | 2023-05-22 10:14:27 +0200
+
+  * Fix CMAKE_BUILD_TYPE_LOWER definition-vs-use ordering problem (Christian Kreibich, Corelight)
+
+    It needs to be defined by the time we create zeek-config, which happens before
+    its current definition. To avoid a redundant TOLOWER when we check for presence
+    of --enable-debug at the beginning, this also switches this to a case-unadjusted
+    comparison to "Debug", which we use elsewhere in the file too.
+
 6.0.0-dev.614 | 2023-05-19 10:51:35 -0700
 
   * Allow plugins to call find_package(Zeek) (Dominik Charousset)
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1c3fa86af0..e08d87d01c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -11,12 +11,8 @@ project(Zeek C CXX)
 
 # We want to set ENABLE_DEBUG to ON by default if the build type is Debug.
 set(ENABLE_DEBUG_DEFAULT OFF)
-if (NOT GENERATOR_IS_MULTI_CONFIG)
-    string(TOLOWER "${CMAKE_BUILD_TYPE}" build_type_lower)
-    if (build_type_lower STREQUAL "debug")
-        set(ENABLE_DEBUG_DEFAULT ON)
-    endif ()
-    unset(build_type_lower)
+if (NOT GENERATOR_IS_MULTI_CONFIG AND CMAKE_BUILD_TYPE STREQUAL "Debug")
+    set(ENABLE_DEBUG_DEFAULT ON)
 endif ()
 
 # On UNIX, install additional Zeek tools by default and build shared objects.
@@ -169,6 +165,8 @@ include(cmake/CommonCMakeConfig.cmake)
 include(cmake/FindClangTidy.cmake)
 include(cmake/CheckCompilerArch.cmake)
 
+string(TOLOWER ${CMAKE_BUILD_TYPE} CMAKE_BUILD_TYPE_LOWER)
+
 # ##############################################################################
 # Main targets and utilities.
 
@@ -1262,7 +1260,6 @@ configure_file(${CMAKE_SOURCE_DIR}/spicy-path.in ${CMAKE_BINARY_DIR}/spicy-path
 configure_file(${CMAKE_SOURCE_DIR}/hilti-cxx-include-dirs.in
                ${CMAKE_BINARY_DIR}/hilti-cxx-include-dirs @ONLY)
 
-string(TOLOWER ${CMAKE_BUILD_TYPE} CMAKE_BUILD_TYPE_LOWER)
 configure_file(${CMAKE_CURRENT_SOURCE_DIR}/zeek-version.h.in
                ${CMAKE_CURRENT_BINARY_DIR}/zeek-version.h)
 install(FILES ${CMAKE_CURRENT_BINARY_DIR}/zeek-version.h DESTINATION include/zeek)
diff --git a/VERSION b/VERSION
index 3012fedbe9..911c1bd9cb 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-6.0.0-dev.614
+6.0.0-dev.617