diff --git a/src/input.c b/src/input.c
index 8c1bb7ef..8ab141fb 100644
--- a/src/input.c
+++ b/src/input.c
@@ -701,6 +701,12 @@ GLFWAPI const char* glfwGetKeyName(int key, int scancode)
 
     if (key != GLFW_KEY_UNKNOWN)
     {
+        if (key < GLFW_KEY_SPACE || key > GLFW_KEY_LAST)
+        {
+            _glfwInputError(GLFW_INVALID_ENUM, "Invalid key %i", key);
+            return NULL;
+        }
+
         if (key != GLFW_KEY_KP_EQUAL &&
             (key < GLFW_KEY_KP_0 || key > GLFW_KEY_KP_ADD) &&
             (key < GLFW_KEY_APOSTROPHE || key > GLFW_KEY_WORLD_2))