diff --git a/kde-modules/KDEInstallDirs.cmake b/kde-modules/KDEInstallDirs.cmake
--- a/kde-modules/KDEInstallDirs.cmake
+++ b/kde-modules/KDEInstallDirs.cmake
@@ -455,7 +455,7 @@
 
 set(_default_KDE_INSTALL_USE_QT_SYS_PATHS OFF)
 if(NOT DEFINED KDE_INSTALL_USE_QT_SYS_PATHS)
-    query_qmake(qt_install_prefix_dir QT_INSTALL_PREFIX)
+    query_qmake(qt_install_prefix_dir QT_INSTALL_PREFIX TRY)
     if(qt_install_prefix_dir STREQUAL "${CMAKE_INSTALL_PREFIX}")
         message(STATUS "Installing in the same prefix as Qt, adopting their path scheme.")
         set(_default_KDE_INSTALL_USE_QT_SYS_PATHS ON)
diff --git a/modules/ECMAddQch.cmake b/modules/ECMAddQch.cmake
--- a/modules/ECMAddQch.cmake
+++ b/modules/ECMAddQch.cmake
@@ -289,7 +289,7 @@
         # get Qt version, if any
         find_package(Qt5Core CONFIG QUIET)
         # lookup tag files
-        query_qmake(qt_docs_dir QT_INSTALL_DOCS)
+        query_qmake(qt_docs_dir QT_INSTALL_DOCS TRY)
         find_path(_qtcoreTagsPath qtcore/qtcore.tags
             PATHS
                 ${qt_docs_dir}
diff --git a/modules/ECMGeneratePriFile.cmake b/modules/ECMGeneratePriFile.cmake
--- a/modules/ECMGeneratePriFile.cmake
+++ b/modules/ECMGeneratePriFile.cmake
@@ -102,7 +102,7 @@
 set(_askqmake OFF)
 if(NOT DEFINED KDE_INSTALL_USE_QT_SYS_PATHS)
     include(ECMQueryQmake)
-    query_qmake(qt_install_prefix_dir QT_INSTALL_PREFIX)
+    query_qmake(qt_install_prefix_dir QT_INSTALL_PREFIX TRY)
     if(qt_install_prefix_dir STREQUAL "${CMAKE_INSTALL_PREFIX}")
         set(_askqmake ON)
     endif()
diff --git a/modules/ECMQueryQmake.cmake b/modules/ECMQueryQmake.cmake
--- a/modules/ECMQueryQmake.cmake
+++ b/modules/ECMQueryQmake.cmake
@@ -9,12 +9,26 @@
 set(QMAKE_EXECUTABLE ${_qmake_executable_default}
     CACHE FILEPATH "Location of the Qt5 qmake executable")
 
+# Helper method
 # This is not public API (yet)!
+# Usage: query_qmake(<result_variable> <qt_variable> [TRY])
+# Passing TRY will result in the method not failing fatal if no qmake executable
+# has been found, but instead simply returning an empty string
 function(query_qmake result_variable qt_variable)
+    set(options TRY)
+    set(oneValueArgs )
+    set(multiValueArgs )
+
+    cmake_parse_arguments(ARGS "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
+
     if(NOT QMAKE_EXECUTABLE)
-        set(${result_variable} "" PARENT_SCOPE)
-        message(WARNING "Should specify a qmake Qt5 binary. Can't check ${qt_variable}")
-        return()
+        if(ARGS_TRY)
+            set(${result_variable} "" PARENT_SCOPE)
+            message(STATUS "No qmake Qt5 binary found. Can't check ${qt_variable}")
+            return()
+        else()
+            message(FATAL_ERROR "No qmake Qt5 binary found. Can't check ${qt_variable} as required")
+        endif()
     endif()
     execute_process(
         COMMAND ${QMAKE_EXECUTABLE} -query "${qt_variable}"