diff --git a/src/glm-test.cpp b/src/glm-test.cpp
index 1f98f2e2..ee6c6498 100644
--- a/src/glm-test.cpp
+++ b/src/glm-test.cpp
@@ -5,6 +5,7 @@
  * http://glm.g-truc.net/0.9.7/index.html.
  */
 
+#define GLM_ENABLE_EXPERIMENTAL // for string_cast
 #include <glm/gtc/matrix_transform.hpp> // glm::translate, glm::rotate, glm::scale, glm::perspective
 #include <glm/mat4x4.hpp> // glm::mat4
 #include <glm/vec3.hpp> // glm::vec3
diff --git a/src/glm.mk b/src/glm.mk
index 966587ef..168a0842 100644
--- a/src/glm.mk
+++ b/src/glm.mk
@@ -4,8 +4,8 @@ PKG             := glm
 $(PKG)_WEBSITE  := https://glm.g-truc.net/
 $(PKG)_DESCR    := GLM - OpenGL Mathematics
 $(PKG)_IGNORE   :=
-$(PKG)_VERSION  := 0.9.7.6
-$(PKG)_CHECKSUM := 872fdea580b69b752562adc60734d7472fd97d5724c4ead585564083deac3953
+$(PKG)_VERSION  := 0.9.9.0
+$(PKG)_CHECKSUM := 514dea9ac0099dc389cf293cf1ab3d97aff080abad55bf79d4ab7ff6895ee69c
 $(PKG)_GH_CONF  := g-truc/glm/tags
 $(PKG)_DEPS     := cc