Index: cmake/OpenCVDetectPython.cmake
===================================================================
--- cmake/OpenCVDetectPython.cmake.orig
+++ cmake/OpenCVDetectPython.cmake
@@ -122,11 +122,12 @@ if(PYTHON_EXECUTABLE)
   if(BUILD_DOCS)
     find_host_program(SPHINX_BUILD sphinx-build)
     if(SPHINX_BUILD)
-        execute_process(COMMAND "${SPHINX_BUILD}"
-                        OUTPUT_QUIET
+        execute_process(COMMAND "${SPHINX_BUILD}" -h
+                        OUTPUT_VARIABLE SPHINX_OUTPUT
                         ERROR_VARIABLE SPHINX_OUTPUT
-                        OUTPUT_STRIP_TRAILING_WHITESPACE)
-        if(SPHINX_OUTPUT MATCHES "Sphinx v([0-9][^ \n]*)")
+                        OUTPUT_STRIP_TRAILING_WHITESPACE
+                        ERROR_STRIP_TRAILING_WHITESPACE)
+        if(SPHINX_OUTPUT MATCHES "Sphinx v([0-9]*[^ \n]*)")
           set(SPHINX_VERSION "${CMAKE_MATCH_1}")
           set(HAVE_SPHINX 1)
           message(STATUS "Found Sphinx ${SPHINX_VERSION}: ${SPHINX_BUILD}")