diff --git a/gli/core/levels.inl b/gli/core/levels.inl
index 0356c0d2..06146376 100644
--- a/gli/core/levels.inl
+++ b/gli/core/levels.inl
@@ -1,5 +1,7 @@
 #include <glm/gtc/integer.hpp>
+#ifndef GLM_ENABLE_EXPERIMENTAL
 #define GLM_ENABLE_EXPERIMENTAL
+#endif
 #include <glm/gtx/component_wise.hpp>
 
 namespace gli
diff --git a/gli/core/sampler.inl b/gli/core/sampler.inl
index e0b64631..c1c88bd8 100644
--- a/gli/core/sampler.inl
+++ b/gli/core/sampler.inl
@@ -1,4 +1,6 @@
+#ifndef GLM_ENABLE_EXPERIMENTAL
 #define GLM_ENABLE_EXPERIMENTAL
+#endif
 #include <glm/gtx/wrap.hpp>
 
 namespace gli{