diff --git a/godoc/analysis/analysis.go b/godoc/analysis/analysis.go
index 936872cc..9fabe118 100644
--- a/godoc/analysis/analysis.go
+++ b/godoc/analysis/analysis.go
@@ -381,6 +381,9 @@ func Run(pta bool, result *Result) {
 	for _, info := range iprog.AllPackages {
 	nextfile:
 		for _, f := range info.Files {
+			if f.Pos() == 0 {
+				continue // e.g. files generated by cgo
+			}
 			abs := iprog.Fset.File(f.Pos()).Name()
 			// Find the root to which this file belongs.
 			for _, root := range roots {
@@ -412,7 +415,8 @@ func Run(pta bool, result *Result) {
 					errors[e.Pos] = append(errors[e.Pos], e.Msg)
 				}
 			default:
-				log.Printf("Error (%T) without position: %v\n", err, err)
+				log.Printf("Package %q has error (%T) without position: %v\n",
+					info.Pkg.Path(), err, err)
 			}
 		}
 	}