diff --git a/src/net/ip_test.go b/src/net/ip_test.go
index 0ef46ee334..46551633ce 100644
--- a/src/net/ip_test.go
+++ b/src/net/ip_test.go
@@ -28,6 +28,10 @@ var parseIPTests = []struct {
 	{"2001:4860:0:2001::68", IP{0x20, 0x01, 0x48, 0x60, 0, 0, 0x20, 0x01, 0, 0, 0, 0, 0, 0, 0x00, 0x68}},
 	{"2001:4860:0000:2001:0000:0000:0000:0068", IP{0x20, 0x01, 0x48, 0x60, 0, 0, 0x20, 0x01, 0, 0, 0, 0, 0, 0, 0x00, 0x68}},
 
+	{"-0.0.0.0", nil},
+	{"0.-1.0.0", nil},
+	{"0.0.-2.0", nil},
+	{"0.0.0.-3", nil},
 	{"127.0.0.256", nil},
 	{"abc", nil},
 	{"123:", nil},
@@ -332,6 +336,12 @@ var parseCIDRTests = []struct {
 	{"192.168.1.1/255.255.255.0", nil, nil, &ParseError{Type: "CIDR address", Text: "192.168.1.1/255.255.255.0"}},
 	{"192.168.1.1/35", nil, nil, &ParseError{Type: "CIDR address", Text: "192.168.1.1/35"}},
 	{"2001:db8::1/-1", nil, nil, &ParseError{Type: "CIDR address", Text: "2001:db8::1/-1"}},
+	{"2001:db8::1/-0", nil, nil, &ParseError{Type: "CIDR address", Text: "2001:db8::1/-0"}},
+	{"-0.0.0.0/32", nil, nil, &ParseError{Type: "CIDR address", Text: "-0.0.0.0/32"}},
+	{"0.-1.0.0/32", nil, nil, &ParseError{Type: "CIDR address", Text: "0.-1.0.0/32"}},
+	{"0.0.-2.0/32", nil, nil, &ParseError{Type: "CIDR address", Text: "0.0.-2.0/32"}},
+	{"0.0.0.-3/32", nil, nil, &ParseError{Type: "CIDR address", Text: "0.0.0.-3/32"}},
+	{"0.0.0.0/-0", nil, nil, &ParseError{Type: "CIDR address", Text: "0.0.0.0/-0"}},
 	{"", nil, nil, &ParseError{Type: "CIDR address", Text: ""}},
 }
 
diff --git a/src/net/parse.go b/src/net/parse.go
index 363c83f6ce..d615eb2b56 100644
--- a/src/net/parse.go
+++ b/src/net/parse.go
@@ -127,26 +127,14 @@ const big = 0xFFFFFF
 // Returns number, characters consumed, success.
 func dtoi(s string) (n int, i int, ok bool) {
 	n = 0
-	neg := false
-	if len(s) > 0 && s[0] == '-' {
-		neg = true
-		s = s[1:]
-	}
 	for i = 0; i < len(s) && '0' <= s[i] && s[i] <= '9'; i++ {
 		n = n*10 + int(s[i]-'0')
 		if n >= big {
-			if neg {
-				return -big, i + 1, false
-			}
 			return big, i, false
 		}
 	}
 	if i == 0 {
-		return 0, i, false
-	}
-	if neg {
-		n = -n
-		i++
+		return 0, 0, false
 	}
 	return n, i, true
 }
diff --git a/src/net/parse_test.go b/src/net/parse_test.go
index 5c1c88cacd..c5f8bfd198 100644
--- a/src/net/parse_test.go
+++ b/src/net/parse_test.go
@@ -86,12 +86,11 @@ func TestDtoi(t *testing.T) {
 		ok  bool
 	}{
 		{"", 0, 0, false},
-
-		{"-123456789", -big, 9, false},
-		{"-1", -1, 2, true},
 		{"0", 0, 1, true},
 		{"65536", 65536, 5, true},
 		{"123456789", big, 8, false},
+		{"-0", 0, 0, false},
+		{"-1234", 0, 0, false},
 	} {
 		n, i, ok := dtoi(tt.in)
 		if n != tt.out || i != tt.off || ok != tt.ok {