diff --git a/multistrap b/multistrap
index af99658..04e1960 100755
--- a/multistrap
+++ b/multistrap
@@ -260,11 +260,14 @@ foreach my $aptsrc (@debootstrap)
 		$mirror = $sources{$aptsrc};
 		$suite = $suites{$aptsrc};
 		$component = (defined $components{$aptsrc}) ? $components{$aptsrc} : "main";
-		print SOURCES<<END;
+		if (defined $mirror and defined $suite)
+		{
+			print SOURCES<<END;
 deb $mirror $suite $component
 deb-src $mirror $suite $component
 END
-		close SOURCES;
+			close SOURCES;
+		}
 	}
 }
 my $k;
@@ -398,11 +401,13 @@ foreach my $aptsrc (@aptsources)
 		$mirror = $sources{$aptsrc};
 		$suite = $suites{$aptsrc};
 		$component = (defined $components{$aptsrc}) ? $components{$aptsrc} : "main";
-		print SOURCES<<END;
+		if (defined $mirror and defined $suite)
+			print SOURCES<<END;
 deb $mirror $suite $component
 deb-src $mirror $suite $component
 END
-		close SOURCES;
+			close SOURCES;
+		}
 	}
 }
 # altered the sources, so get apt to update.