diff --git a/user/user.go b/user/user.go
index 1fd9a08..7bc62fd 100644
--- a/user/user.go
+++ b/user/user.go
@@ -56,13 +56,14 @@ type IDMap struct {
 	Count    int64
 }
 
-func parseLine(line []byte, v ...any) {
-	parseParts(bytes.Split(line, []byte(":")), v...)
+func parseLine(line []byte, v ...any) error {
+	return parseParts(bytes.Split(line, []byte(":")), v...)
 }
 
-func parseParts(parts [][]byte, v ...any) {
+func parseParts(parts [][]byte, v ...any) error {
 	if len(parts) == 0 {
-		return
+		// TODO(thaJeztah); do we need an "ok" return so that we can skip these in loops?
+		return nil
 	}
 
 	for i, p := range parts {
@@ -78,10 +79,24 @@ func parseParts(parts [][]byte, v ...any) {
 		case *string:
 			*e = string(p)
 		case *int:
-			// "numbers", with conversion errors ignored because of some misbehaving configuration files.
-			*e, _ = strconv.Atoi(string(p))
+			if len(p) != 0 {
+				n, ok, err := parseNumeric(string(p))
+				if err != nil {
+					return fmt.Errorf("parsing integer field %d: %w", i, err)
+				}
+				if !ok {
+					return fmt.Errorf("parsing integer field %d: %q is not numeric", i, p)
+				}
+				*e = n
+			}
 		case *int64:
-			*e, _ = strconv.ParseInt(string(p), 10, 64)
+			if len(p) != 0 {
+				n, err := strconv.ParseInt(string(p), 10, 64)
+				if err != nil {
+					return fmt.Errorf("parsing integer field %d: %w", i, err)
+				}
+				*e = n
+			}
 		case *[]string:
 			// Comma-separated lists.
 			if len(p) != 0 {
@@ -94,6 +109,7 @@ func parseParts(parts [][]byte, v ...any) {
 			panic(fmt.Sprintf("parseLine only accepts {*string, *int, *int64, *[]string} as arguments! %#v is not a pointer!", e))
 		}
 	}
+	return nil
 }
 
 func ParsePasswdFile(path string) ([]User, error) {
@@ -135,7 +151,11 @@ func ParsePasswdFilter(r io.Reader, filter func(User) bool) ([]User, error) {
 		//  root:x:0:0:root:/root:/bin/bash
 		//  adm:x:3:4:adm:/var/adm:/bin/false
 		p := User{}
-		parseLine(line, &p.Name, &p.Pass, &p.Uid, &p.Gid, &p.Gecos, &p.Home, &p.Shell)
+		if err := parseLine(line, &p.Name, &p.Pass, &p.Uid, &p.Gid, &p.Gecos, &p.Home, &p.Shell); err != nil {
+			// Skip malformed lines, and don't consider them.
+			// return nil, fmt.Errorf("invalid line (%q): %w", string(line), err)
+			continue
+		}
 
 		if filter == nil || filter(p) {
 			out = append(out, p)
@@ -194,7 +214,11 @@ func ParseGroupFilter(r io.Reader, filter func(Group) bool) ([]Group, error) {
 		//  root:x:0:root
 		//  adm:x:4:root,adm,daemon
 		p := Group{}
-		parseLine(line, &p.Name, &p.Pass, &p.Gid, &p.List)
+		if err := parseLine(line, &p.Name, &p.Pass, &p.Gid, &p.List); err != nil {
+			// Skip malformed lines, and don't consider them.
+			// return nil, fmt.Errorf("invalid line (%q): %w", string(line), err)
+			continue
+		}
 
 		if filter == nil || filter(p) {
 			out = append(out, p)
@@ -539,7 +563,11 @@ func ParseSubIDFilter(r io.Reader, filter func(SubID) bool) ([]SubID, error) {
 
 		// see: man 5 subuid
 		p := SubID{}
-		parseLine(line, &p.Name, &p.SubID, &p.Count)
+		if err := parseLine(line, &p.Name, &p.SubID, &p.Count); err != nil {
+			// Skip malformed lines, and don't consider them.
+			// return nil, fmt.Errorf("invalid line (%q): %w", string(line), err)
+			return nil, err
+		}
 
 		if filter == nil || filter(p) {
 			out = append(out, p)
@@ -587,7 +615,11 @@ func ParseIDMapFilter(r io.Reader, filter func(IDMap) bool) ([]IDMap, error) {
 
 		// see: man 7 user_namespaces
 		p := IDMap{}
-		parseParts(bytes.Fields(line), &p.ID, &p.ParentID, &p.Count)
+		if err := parseParts(bytes.Fields(line), &p.ID, &p.ParentID, &p.Count); err != nil {
+			// Skip malformed lines, and don't consider them.
+			// return nil, fmt.Errorf("invalid line (%q): %w", string(line), err)
+			continue
+		}
 
 		if filter == nil || filter(p) {
 			out = append(out, p)
diff --git a/user/user_test.go b/user/user_test.go
index e5f599a..5102451 100644
--- a/user/user_test.go
+++ b/user/user_test.go
@@ -21,42 +21,66 @@ func TestParseLine(t *testing.T) {
 		d    int
 	)
 
-	parseLine([]byte(""), &a, &b)
+	err := parseLine([]byte(""), &a, &b)
+	if err != nil {
+		t.Fatal(err)
+	}
 	if a != "" || b != "" {
 		t.Fatalf("a and b should be empty ('%v', '%v')", a, b)
 	}
 
-	parseLine([]byte("a"), &a, &b)
+	err = parseLine([]byte("a"), &a, &b)
+	if err != nil {
+		t.Fatal(err)
+	}
 	if a != "a" || b != "" {
 		t.Fatalf("a should be 'a' and b should be empty ('%v', '%v')", a, b)
 	}
 
-	parseLine([]byte("bad boys:corny cows"), &a, &b)
+	err = parseLine([]byte("bad boys:corny cows"), &a, &b)
+	if err != nil {
+		t.Fatal(err)
+	}
 	if a != "bad boys" || b != "corny cows" {
 		t.Fatalf("a should be 'bad boys' and b should be 'corny cows' ('%v', '%v')", a, b)
 	}
 
-	parseLine([]byte(""), &c)
+	err = parseLine([]byte(""), &c)
+	if err != nil {
+		t.Fatal(err)
+	}
 	if len(c) != 0 {
 		t.Fatalf("c should be empty (%#v)", c)
 	}
 
-	parseLine([]byte("d,e,f:g:h:i,j,k"), &c, &a, &b, &c)
+	err = parseLine([]byte("d,e,f:g:h:i,j,k"), &c, &a, &b, &c)
+	if err != nil {
+		t.Fatal(err)
+	}
 	if a != "g" || b != "h" || len(c) != 3 || c[0] != "i" || c[1] != "j" || c[2] != "k" {
 		t.Fatalf("a should be 'g', b should be 'h', and c should be ['i','j','k'] ('%v', '%v', '%#v')", a, b, c)
 	}
 
-	parseLine([]byte("::::::::::"), &a, &b, &c)
+	err = parseLine([]byte("::::::::::"), &a, &b, &c)
+	if err != nil {
+		t.Fatal(err)
+	}
 	if a != "" || b != "" || len(c) != 0 {
 		t.Fatalf("a, b, and c should all be empty ('%v', '%v', '%#v')", a, b, c)
 	}
 
-	parseLine([]byte("not a number"), &d)
+	err = parseLine([]byte("not a number"), &d)
+	if err == nil {
+		t.Fatal("expected an error")
+	}
 	if d != 0 {
 		t.Fatalf("d should be 0 (%v)", d)
 	}
 
-	parseLine([]byte("b:12:c"), &a, &d, &b)
+	err = parseLine([]byte("b:12:c"), &a, &d, &b)
+	if err != nil {
+		t.Fatal(err)
+	}
 	if a != "b" || b != "c" || d != 12 {
 		t.Fatalf("a should be 'b' and b should be 'c', and d should be 12 ('%v', '%v', %v)", a, b, d)
 	}