diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index cf0cec8d3cb82e..3b02781bf1cdb6 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -3090,6 +3090,26 @@ __gitcomp_directories ()
 		# No possible further completions any deeper, so assume we're at
 		# a leaf directory and just consider it complete
 		__gitcomp_direct_append "$cur "
+	elif [[ $_found == 0 ]]; then
+		# No possible completions found.  Avoid falling back to
+		# bash's default file and directory completion, because all
+		# valid completions have already been searched and the
+		# fallbacks can do nothing but mislead.  In fact, they can
+		# mislead in three different ways:
+		#    1) Fallback file completion makes no sense when asking
+		#       for directory completions, as this function does.
+		#    2) Fallback directory completion is bad because
+		#       e.g. "/pro" is invalid and should NOT complete to
+		#       "/proc".
+		#    3) Fallback file/directory completion only completes
+		#       on paths that exist in the current working tree,
+		#       i.e. which are *already* part of their
+		#       sparse-checkout.  Thus, normal file and directory
+		#       completion is always useless for "git
+		#       sparse-checkout add" and is also probelmatic for
+		#       "git sparse-checkout set" unless using it to
+		#       strictly narrow the checkout.
+		COMPREPLY=( "" )
 	fi
 }