diff --git a/openapi2conv/issue440_test.go b/openapi2conv/issue440_test.go
new file mode 100644
index 000000000..24f7a29e9
--- /dev/null
+++ b/openapi2conv/issue440_test.go
@@ -0,0 +1,48 @@
+package openapi2conv
+
+import (
+	"context"
+	"encoding/json"
+	"os"
+	"testing"
+
+	"github.com/getkin/kin-openapi/openapi2"
+	"github.com/getkin/kin-openapi/openapi3"
+	"github.com/stretchr/testify/require"
+)
+
+func TestIssue440(t *testing.T) {
+	doc2file, err := os.Open("testdata/swagger.json")
+	require.NoError(t, err)
+	defer doc2file.Close()
+	var doc2 openapi2.T
+	err = json.NewDecoder(doc2file).Decode(&doc2)
+	require.NoError(t, err)
+
+	doc3, err := ToV3(&doc2)
+	require.NoError(t, err)
+	err = doc3.Validate(context.Background())
+	require.NoError(t, err)
+	require.Equal(t, openapi3.Servers{
+		{URL: "https://petstore.swagger.io/v2"},
+		{URL: "http://petstore.swagger.io/v2"},
+	}, doc3.Servers)
+
+	doc2.Host = "your-bot-domain.de"
+	doc2.Schemes = nil
+	doc2.BasePath = ""
+	doc3, err = ToV3(&doc2)
+	require.NoError(t, err)
+	err = doc3.Validate(context.Background())
+	require.NoError(t, err)
+	require.Equal(t, openapi3.Servers{
+		{URL: "https://your-bot-domain.de/"},
+	}, doc3.Servers)
+
+	doc2.Host = "https://your-bot-domain.de"
+	doc2.Schemes = nil
+	doc2.BasePath = ""
+	doc3, err = ToV3(&doc2)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), `invalid host`)
+}
diff --git a/openapi2conv/openapi2_conv.go b/openapi2conv/openapi2_conv.go
index 6877e88e8..e9f3164c0 100644
--- a/openapi2conv/openapi2_conv.go
+++ b/openapi2conv/openapi2_conv.go
@@ -26,11 +26,18 @@ func ToV3(doc2 *openapi2.T) (*openapi3.T, error) {
 	}
 
 	if host := doc2.Host; host != "" {
+		if strings.Contains(host, "/") {
+			err := fmt.Errorf("invalid host %q. This MUST be the host only and does not include the scheme nor sub-paths.", host)
+			return nil, err
+		}
 		schemes := doc2.Schemes
 		if len(schemes) == 0 {
-			schemes = []string{"https://"}
+			schemes = []string{"https"}
 		}
 		basePath := doc2.BasePath
+		if basePath == "" {
+			basePath = "/"
+		}
 		for _, scheme := range schemes {
 			u := url.URL{
 				Scheme: scheme,
diff --git a/openapi2conv/openapi2_conv_test.go b/openapi2conv/openapi2_conv_test.go
index adb9b0814..a8322698f 100644
--- a/openapi2conv/openapi2_conv_test.go
+++ b/openapi2conv/openapi2_conv_test.go
@@ -23,9 +23,9 @@ func TestConvOpenAPIV3ToV2(t *testing.T) {
 		require.NoError(t, err)
 	}
 
-	spec2, err := FromV3(&doc3)
+	doc2, err := FromV3(&doc3)
 	require.NoError(t, err)
-	data, err := json.Marshal(spec2)
+	data, err := json.Marshal(doc2)
 	require.NoError(t, err)
 	require.JSONEq(t, exampleV2, string(data))
 }
@@ -35,11 +35,11 @@ func TestConvOpenAPIV2ToV3(t *testing.T) {
 	err := json.Unmarshal([]byte(exampleV2), &doc2)
 	require.NoError(t, err)
 
-	spec3, err := ToV3(&doc2)
+	doc3, err := ToV3(&doc2)
 	require.NoError(t, err)
-	err = spec3.Validate(context.Background())
+	err = doc3.Validate(context.Background())
 	require.NoError(t, err)
-	data, err := json.Marshal(spec3)
+	data, err := json.Marshal(doc3)
 	require.NoError(t, err)
 	require.JSONEq(t, exampleV3, string(data))
 }
diff --git a/openapi2conv/testdata/swagger.json b/openapi2conv/testdata/swagger.json
new file mode 120000
index 000000000..c211aa245
--- /dev/null
+++ b/openapi2conv/testdata/swagger.json
@@ -0,0 +1 @@
+../../openapi2/testdata/swagger.json
\ No newline at end of file
diff --git a/openapi3/schema.go b/openapi3/schema.go
index 3793ac19d..443f71980 100644
--- a/openapi3/schema.go
+++ b/openapi3/schema.go
@@ -1176,7 +1176,7 @@ func (schema *Schema) visitJSONString(settings *schemaValidationSettings, value
 			Value:       value,
 			Schema:      schema,
 			SchemaField: "pattern",
-			Reason:      fmt.Sprintf("string doesn't match the regular expression \"%s\"", schema.Pattern),
+			Reason:      fmt.Sprintf(`string doesn't match the regular expression "%s"`, schema.Pattern),
 		}
 		if !settings.multiError {
 			return err
@@ -1191,7 +1191,7 @@ func (schema *Schema) visitJSONString(settings *schemaValidationSettings, value
 			switch {
 			case f.regexp != nil && f.callback == nil:
 				if cp := f.regexp; !cp.MatchString(value) {
-					formatErr = fmt.Sprintf("string doesn't match the format %q (regular expression \"%s\")", format, cp.String())
+					formatErr = fmt.Sprintf(`string doesn't match the format %q (regular expression "%s")`, format, cp.String())
 				}
 			case f.regexp == nil && f.callback != nil:
 				if err := f.callback(value); err != nil {