diff --git a/build/cmake/modules/FindGTK3.cmake b/build/cmake/modules/FindGTK3.cmake
index 5c35029a81..8fee6f9f41 100644
--- a/build/cmake/modules/FindGTK3.cmake
+++ b/build/cmake/modules/FindGTK3.cmake
@@ -46,5 +46,6 @@ endif ()
 include(CheckSymbolExists)
 set(CMAKE_REQUIRED_INCLUDES ${GTK3_INCLUDE_DIRS})
 check_symbol_exists(GDK_WINDOWING_WAYLAND "gdk/gdk.h" wxHAVE_GDK_WAYLAND)
+check_symbol_exists(GDK_WINDOWING_X11 "gdk/gdk.h" wxHAVE_GDK_X11)
 include(FindPackageHandleStandardArgs)
 FIND_PACKAGE_HANDLE_STANDARD_ARGS(GTK3 DEFAULT_MSG GTK3_INCLUDE_DIRS GTK3_LIBRARIES VERSION_OK)
diff --git a/build/cmake/toolkit.cmake b/build/cmake/toolkit.cmake
index 577d3c8661..bcbbd75491 100644
--- a/build/cmake/toolkit.cmake
+++ b/build/cmake/toolkit.cmake
@@ -69,12 +69,6 @@ set(wxTOOLKIT_INCLUDE_DIRS)
 set(wxTOOLKIT_LIBRARIES)
 set(wxTOOLKIT_VERSION)
 
-if(UNIX AND NOT APPLE AND NOT WIN32)
-    find_package(X11 REQUIRED)
-    list(APPEND wxTOOLKIT_INCLUDE_DIRS ${X11_INCLUDE_DIR})
-    list(APPEND wxTOOLKIT_LIBRARIES ${X11_LIBRARIES})
-endif()
-
 if(WXGTK)
     if(WXGTK4)
         set(gtk_lib GTK4)
@@ -121,6 +115,15 @@ if(WXGTK)
     endif()
 endif()
 
+# We need X11 for non-GTK Unix ports (X11, Motif) and for GTK with X11
+# support, but not for Wayland-only GTK (which is why we have to do this after
+# find_package(GTKx) above, as this is what sets wxHAVE_GDK_X11).
+if(UNIX AND NOT APPLE AND NOT WIN32 AND (WXX11 OR WXMOTIF OR (WXGTK AND wxHAVE_GDK_X11)))
+    find_package(X11 REQUIRED)
+    list(APPEND wxTOOLKIT_INCLUDE_DIRS ${X11_INCLUDE_DIR})
+    list(APPEND wxTOOLKIT_LIBRARIES ${X11_LIBRARIES})
+endif()
+
 if(WXQT)
     set(QT_COMPONENTS Core Widgets Gui OpenGL Test)
     foreach(QT_COMPONENT ${QT_COMPONENTS})