diff --git a/src/null_window.c b/src/null_window.c
index 1fc861b5..a22fc1a4 100644
--- a/src/null_window.c
+++ b/src/null_window.c
@@ -30,6 +30,7 @@
 #include "internal.h"
 
 #include <stdlib.h>
+#include <string.h>
 
 static void applySizeLimits(_GLFWwindow* window, int* width, int* height)
 {
diff --git a/src/wl_window.c b/src/wl_window.c
index 2b05af60..7b8a813c 100644
--- a/src/wl_window.c
+++ b/src/wl_window.c
@@ -2775,9 +2775,10 @@ const char* _glfwGetClipboardStringWayland(void)
     return _glfw.wl.clipboardString;
 }
 
-void _glfwSetThemeWayland(_GLFWwindow* window, _GLFWtheme* theme)
+void _glfwSetThemeWayland(_GLFWwindow* window, const _GLFWtheme* theme)
 {
     _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED, NULL);
+    // TODO: implement
 }
 
 _GLFWtheme* _glfwGetThemeWayland(_GLFWwindow* window, int inlineDefaults)
diff --git a/src/x11_window.c b/src/x11_window.c
index 9ee0f2ee..28320dea 100644
--- a/src/x11_window.c
+++ b/src/x11_window.c
@@ -3085,6 +3085,7 @@ const char* _glfwGetClipboardStringX11(void)
 void _glfwSetThemeX11(_GLFWwindow* window, const _GLFWtheme* theme)
 {
     _glfwInputError(GLFW_FEATURE_UNIMPLEMENTED, NULL);
+    // TODO: implement
 }
 
 _GLFWtheme* _glfwGetThemeX11(_GLFWwindow* window, int inlineDefaults)