diff --git a/tests/libtest/CMakeLists.txt b/tests/libtest/CMakeLists.txt
index f5f6a0d10c..60b1bd42f4 100644
--- a/tests/libtest/CMakeLists.txt
+++ b/tests/libtest/CMakeLists.txt
@@ -27,7 +27,9 @@
 curl_transform_makefile_inc("Makefile.inc" "${CMAKE_CURRENT_BINARY_DIR}/Makefile.inc.cmake")
 include("${CMAKE_CURRENT_BINARY_DIR}/Makefile.inc.cmake")
 
-set_source_files_properties("../../lib/curl_multibyte.c" PROPERTIES SKIP_UNITY_BUILD_INCLUSION ON)
+if(ENABLE_CURLDEBUG)
+  set_source_files_properties("../../lib/curl_multibyte.c" PROPERTIES SKIP_UNITY_BUILD_INCLUSION ON)
+endif()
 
 add_custom_command(
   OUTPUT "lib1521.c"
diff --git a/tests/server/CMakeLists.txt b/tests/server/CMakeLists.txt
index 3b18bba4c3..b7bd88151e 100644
--- a/tests/server/CMakeLists.txt
+++ b/tests/server/CMakeLists.txt
@@ -26,7 +26,9 @@
 curl_transform_makefile_inc("Makefile.inc" "${CMAKE_CURRENT_BINARY_DIR}/Makefile.inc.cmake")
 include("${CMAKE_CURRENT_BINARY_DIR}/Makefile.inc.cmake")
 
-set_source_files_properties("../../lib/memdebug.c" "../../lib/curl_multibyte.c" PROPERTIES SKIP_UNITY_BUILD_INCLUSION ON)
+if(ENABLE_CURLDEBUG)
+  set_source_files_properties("../../lib/memdebug.c" "../../lib/curl_multibyte.c" PROPERTIES SKIP_UNITY_BUILD_INCLUSION ON)
+endif()
 
 foreach(_target IN LISTS noinst_PROGRAMS)
   set(_target_name "${_target}")