diff --git a/scripts/CMakeLists.txt b/scripts/CMakeLists.txt
index 1f93ddc81d..95a01b5068 100644
--- a/scripts/CMakeLists.txt
+++ b/scripts/CMakeLists.txt
@@ -52,27 +52,29 @@ if(CURL_COMPLETION_FISH OR
 
     if(NOT CURL_DISABLE_INSTALL)
       if(NOT CMAKE_CROSSCOMPILING)
-        if(NOT CURL_COMPLETION_FISH_DIR)
-          find_package(PkgConfig QUIET)
-          pkg_get_variable(CURL_COMPLETION_FISH_DIR "fish" "completionsdir")
-          if(NOT _pkg_fish_completionsdir)
-            include(GNUInstallDirs)
-            if(CMAKE_INSTALL_DATAROOTDIR)
-              set(CURL_COMPLETION_FISH_DIR "${CMAKE_INSTALL_DATAROOTDIR}/fish/vendor_completions.d")
+        if(CURL_COMPLETION_FISH)
+          if(NOT CURL_COMPLETION_FISH_DIR)
+            find_package(PkgConfig QUIET)
+            pkg_get_variable(CURL_COMPLETION_FISH_DIR "fish" "completionsdir")
+            if(NOT _pkg_fish_completionsdir)
+              if(CMAKE_INSTALL_DATAROOTDIR)
+                set(CURL_COMPLETION_FISH_DIR "${CMAKE_INSTALL_DATAROOTDIR}/fish/vendor_completions.d")
+              endif()
             endif()
           endif()
-        endif()
-        if(NOT CURL_COMPLETION_ZSH_DIR)
-          include(GNUInstallDirs)
-          if(CMAKE_INSTALL_DATAROOTDIR)
-            set(CURL_COMPLETION_ZSH_DIR "${CMAKE_INSTALL_DATAROOTDIR}/zsh/site-functions")
+          if(CURL_COMPLETION_FISH_DIR)
+            install(FILES "${_completion_fish}" DESTINATION "${CURL_COMPLETION_FISH_DIR}")
           endif()
         endif()
-        if(CURL_COMPLETION_FISH_DIR)
-          install(FILES "${_completion_fish}" DESTINATION "${CURL_COMPLETION_FISH_DIR}")
-        endif()
-        if(CURL_COMPLETION_ZSH_DIR)
-          install(FILES "${_completion_zsh}" DESTINATION "${CURL_COMPLETION_ZSH_DIR}")
+        if(CURL_COMPLETION_ZSH)
+          if(NOT CURL_COMPLETION_ZSH_DIR)
+            if(CMAKE_INSTALL_DATAROOTDIR)
+              set(CURL_COMPLETION_ZSH_DIR "${CMAKE_INSTALL_DATAROOTDIR}/zsh/site-functions")
+            endif()
+          endif()
+          if(CURL_COMPLETION_ZSH_DIR)
+            install(FILES "${_completion_zsh}" DESTINATION "${CURL_COMPLETION_ZSH_DIR}")
+          endif()
         endif()
       else()
         message(STATUS "We cannot install completion scripts when cross-compiling")