Use compgen -W $cur instead of grepping $cur in make completion.

bash_completion

@@ -3037,10 +3037,10 @@ _make()
 		[ -n "$makef" ] && makef="-f ${makef}"
 		[ -n "$makef_dir" ] && makef_dir="-C ${makef_dir}"
 		
-		COMPREPLY=( $( make -qp $makef $makef_dir 2>/dev/null | \
+		COMPREPLY=( $( compgen -W "$( make -qp $makef $makef_dir 2>/dev/null | \
 					awk -F':' '/^[a-zA-Z0-9][^$#\/\t=]*:([^=]|$)/ \
-					{split($1,A,/ /);for(i in A)print A[i]}' | \
-					command grep "^$cur" ))
+					{split($1,A,/ /);for(i in A)print A[i]}' )" \
+					-- $cur ) )
 
 	fi
 } &&