diff --git a/CMake/FindBreathe.cmake b/CMake/FindBreathe.cmake
index 0ea2ed9..1009b75 100644
--- a/CMake/FindBreathe.cmake
+++ b/CMake/FindBreathe.cmake
@@ -1,5 +1,5 @@
 # FindBreathe.cmake
-# Copyright (C) 2021 Manuel Sainz de Baranda y Goñi.
+# Copyright (C) 2021-2022 Manuel Sainz de Baranda y Goñi.
 # This "find module" is DISTRIBUTED AS PUBLIC DOMAIN. No restrictions apply.
 
 include(FindPackageHandleStandardArgs)
@@ -17,6 +17,8 @@ if(BREATHE_APIDOC_EXECUTABLE)
 	if("${_output}" MATCHES ".* ([^\n]+)\n")
 		set(BREATHE_APIDOC_VERSION "${CMAKE_MATCH_1}")
 	endif()
+
+	unset(_output)
 endif()
 
 find_package_handle_standard_args(
diff --git a/CMake/FindSphinx.cmake b/CMake/FindSphinx.cmake
index f22cd50..ad09613 100644
--- a/CMake/FindSphinx.cmake
+++ b/CMake/FindSphinx.cmake
@@ -1,5 +1,5 @@
 # FindSphinx.cmake
-# Copyright (C) 2021 Manuel Sainz de Baranda y Goñi.
+# Copyright (C) 2021-2022 Manuel Sainz de Baranda y Goñi.
 # This "find module" is DISTRIBUTED AS PUBLIC DOMAIN. No restrictions apply.
 
 include(FindPackageHandleStandardArgs)
@@ -17,6 +17,8 @@ if(SPHINX_BUILD_EXECUTABLE)
 	if("${_output}" MATCHES ".* ([^\n]+)\n")
 		set(SPHINX_BUILD_VERSION "${CMAKE_MATCH_1}")
 	endif()
+
+	unset(_output)
 endif()
 
 find_package_handle_standard_args(