diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,8 +7,13 @@
 find_package(ECM 0.0.9 REQUIRED NO_MODULE)
 include(FeatureSummary)
 
-set(WITH_GTK3_VERSION 3.18 CACHE STRING
-    "Use the theme for the specified GTK+3 version (default: 3.18)")
+find_package(GTKEngine)
+
+find_package(PkgConfig)
+pkg_check_modules(PKG_GTK REQUIRED gtk+-3.0)
+
+set(WITH_GTK3_VERSION ${PKG_GTK_VERSION} CACHE STRING
+    "Use the theme for the specified GTK+3 version")
 
 set(CMAKE_MODULE_PATH ${ECM_MODULE_PATH} ${ECM_KDE_MODULE_DIR} "${CMAKE_SOURCE_DIR}/cmake")
 include(KDEInstallDirs)
@@ -25,6 +30,4 @@
 add_subdirectory(Breeze-gtk)
 add_subdirectory(kconf_update)
 
-find_package(GTKEngine)
-
 feature_summary(WHAT ALL INCLUDE_QUIET_PACKAGES FATAL_ON_MISSING_REQUIRED_PACKAGES)