diff --git a/src/csync/CMakeLists.txt b/src/csync/CMakeLists.txt
index 7f0740a72f..cbb8f73d6d 100644
--- a/src/csync/CMakeLists.txt
+++ b/src/csync/CMakeLists.txt
@@ -50,10 +50,6 @@ else()
     )
 endif()
 
-if(NOT HAVE_ASPRINTF AND NOT HAVE___MINGW_ASPRINTF)
-    list(APPEND csync_SRCS std/asprintf.c)
-endif()
-
 if (USE_OUR_OWN_SQLITE3)
     list(APPEND csync_SRCS ${SQLITE3_SOURCE})
 endif()
diff --git a/test/csync/CMakeLists.txt b/test/csync/CMakeLists.txt
index 5a8336c15a..8e0b3c54d4 100644
--- a/test/csync/CMakeLists.txt
+++ b/test/csync/CMakeLists.txt
@@ -25,6 +25,10 @@ add_cmocka_test(check_std_c_str std_tests/check_std_c_str.c ${TEST_TARGET_LIBRAR
 # vio
 add_cmocka_test(check_vio_ext vio_tests/check_vio_ext.cpp ${TEST_TARGET_LIBRARIES})
 
+if(NOT HAVE_ASPRINTF AND NOT HAVE___MINGW_ASPRINTF)
+    target_sources(check_vio_ext PRIVATE ${PROJECT_SOURCE_DIR}/src/csync/std/asprintf.c)
+endif()
+
 # encoding
 add_cmocka_test(check_encoding_functions encoding_tests/check_encoding.cpp ${TEST_TARGET_LIBRARIES})