diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index d6d27ff..4ab1249 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -13,7 +13,7 @@ SET(GUI_TESTS
 ADD_DEFINITIONS(-DTESTDATA_DIR="${PROJECT_SOURCE_DIR}/testdata")
 
 FOREACH(HEADER ${LIBRARY_HEADERS})
-	STRING(MAKE_C_IDENTIFIER ${HEADER} HEADER_NORMALIZED)
+	STRING(REGEX REPLACE [^a-zA-Z0-9] _ HEADER_NORMALIZED ${HEADER})
 	CONFIGURE_FILE(header_test.cc.in ${HEADER_NORMALIZED}_test.cc)
 	ADD_EXECUTABLE(${HEADER_NORMALIZED}_test ${HEADER_NORMALIZED}_test.cc)
 ENDFOREACH(HEADER ${TESTS})