diff --git a/test/core/core_force_cxx03.cpp b/test/core/core_force_cxx03.cpp
index e71e00cd..fc6e9c5d 100644
--- a/test/core/core_force_cxx03.cpp
+++ b/test/core/core_force_cxx03.cpp
@@ -1,4 +1,6 @@
-#define GLM_FORCE_CXX03
+#ifndef GLM_FORCE_CXX03
+#	define GLM_FORCE_CXX03
+#endif
 
 #include <glm/glm.hpp>
 #include <glm/ext.hpp>
diff --git a/test/core/core_force_cxx11.cpp b/test/core/core_force_cxx11.cpp
index 610ea344..cc57e08a 100644
--- a/test/core/core_force_cxx11.cpp
+++ b/test/core/core_force_cxx11.cpp
@@ -1,4 +1,6 @@
-#define GLM_FORCE_CXX11
+#ifndef GLM_FORCE_CXX11
+#	define GLM_FORCE_CXX11
+#endif
 
 #include <glm/glm.hpp>
 #include <glm/ext.hpp>
diff --git a/test/core/core_force_cxx98.cpp b/test/core/core_force_cxx98.cpp
index 56422e48..42a5c259 100644
--- a/test/core/core_force_cxx98.cpp
+++ b/test/core/core_force_cxx98.cpp
@@ -1,4 +1,6 @@
-#define GLM_FORCE_CXX98
+#ifndef GLM_FORCE_CXX98
+#	define GLM_FORCE_CXX98
+#endif
 
 #include <glm/glm.hpp>
 #include <glm/ext.hpp>