diff --git a/acme/types.go b/acme/types.go
index e751bf5..eaae452 100644
--- a/acme/types.go
+++ b/acme/types.go
@@ -57,6 +57,32 @@ var (
 	ErrNoAccount = errors.New("acme: account does not exist")
 )
 
+// A Subproblem describes an ACME subproblem as reported in an Error.
+type Subproblem struct {
+	// Type is a URI reference that identifies the problem type,
+	// typically in a "urn:acme:error:xxx" form.
+	Type string
+	// Detail is a human-readable explanation specific to this occurrence of the problem.
+	Detail string
+	// Instance indicates a URL that the client should direct a human user to visit
+	// in order for instructions on how to agree to the updated Terms of Service.
+	// In such an event CA sets StatusCode to 403, Type to
+	// "urn:ietf:params:acme:error:userActionRequired", and adds a Link header with relation
+	// "terms-of-service" containing the latest TOS URL.
+	Instance string
+	// Identifier may contain the ACME identifier that the error is for.
+	Identifier *AuthzID
+}
+
+func (sp Subproblem) String() string {
+	str := fmt.Sprintf("%s: ", sp.Type)
+	if sp.Identifier != nil {
+		str += fmt.Sprintf("[%s: %s] ", sp.Identifier.Type, sp.Identifier.Value)
+	}
+	str += sp.Detail
+	return str
+}
+
 // Error is an ACME error, defined in Problem Details for HTTP APIs doc
 // http://tools.ietf.org/html/draft-ietf-appsawg-http-problem.
 type Error struct {
@@ -76,10 +102,21 @@ type Error struct {
 	// Header is the original server error response headers.
 	// It may be nil.
 	Header http.Header
+	// Subproblems may contain more detailed information about the individual problems
+	// that caused the error. This field is only sent by RFC 8555 compatible ACME
+	// servers. Defined in RFC 8555 Section 6.7.1.
+	Subproblems []Subproblem
 }
 
 func (e *Error) Error() string {
-	return fmt.Sprintf("%d %s: %s", e.StatusCode, e.ProblemType, e.Detail)
+	str := fmt.Sprintf("%d %s: %s", e.StatusCode, e.ProblemType, e.Detail)
+	if len(e.Subproblems) > 0 {
+		str += fmt.Sprintf("; subproblems:")
+		for _, sp := range e.Subproblems {
+			str += fmt.Sprintf("\n\t%s", sp)
+		}
+	}
+	return str
 }
 
 // AuthorizationError indicates that an authorization for an identifier
@@ -533,20 +570,23 @@ func (c *wireChallenge) challenge() *Challenge {
 // wireError is a subset of fields of the Problem Details object
 // as described in https://tools.ietf.org/html/rfc7807#section-3.1.
 type wireError struct {
-	Status   int
-	Type     string
-	Detail   string
-	Instance string
+	Status      int
+	Type        string
+	Detail      string
+	Instance    string
+	Subproblems []Subproblem
 }
 
 func (e *wireError) error(h http.Header) *Error {
-	return &Error{
+	err := &Error{
 		StatusCode:  e.Status,
 		ProblemType: e.Type,
 		Detail:      e.Detail,
 		Instance:    e.Instance,
 		Header:      h,
+		Subproblems: e.Subproblems,
 	}
+	return err
 }
 
 // CertOption is an optional argument type for the TLS ChallengeCert methods for
diff --git a/acme/types_test.go b/acme/types_test.go
index 9ed7753..59ce7e7 100644
--- a/acme/types_test.go
+++ b/acme/types_test.go
@@ -7,6 +7,7 @@ package acme
 import (
 	"errors"
 	"net/http"
+	"reflect"
 	"testing"
 	"time"
 )
@@ -116,3 +117,103 @@ func TestAuthorizationError(t *testing.T) {
 		}
 	}
 }
+
+func TestSubproblems(t *testing.T) {
+	tests := []struct {
+		wire        wireError
+		expectedOut Error
+	}{
+		{
+			wire: wireError{
+				Status: 1,
+				Type:   "urn:error",
+				Detail: "it's an error",
+			},
+			expectedOut: Error{
+				StatusCode:  1,
+				ProblemType: "urn:error",
+				Detail:      "it's an error",
+			},
+		},
+		{
+			wire: wireError{
+				Status: 1,
+				Type:   "urn:error",
+				Detail: "it's an error",
+				Subproblems: []Subproblem{
+					{
+						Type:   "urn:error:sub",
+						Detail: "it's a subproblem",
+					},
+				},
+			},
+			expectedOut: Error{
+				StatusCode:  1,
+				ProblemType: "urn:error",
+				Detail:      "it's an error",
+				Subproblems: []Subproblem{
+					{
+						Type:   "urn:error:sub",
+						Detail: "it's a subproblem",
+					},
+				},
+			},
+		},
+		{
+			wire: wireError{
+				Status: 1,
+				Type:   "urn:error",
+				Detail: "it's an error",
+				Subproblems: []Subproblem{
+					{
+						Type:       "urn:error:sub",
+						Detail:     "it's a subproblem",
+						Identifier: &AuthzID{Type: "dns", Value: "example"},
+					},
+				},
+			},
+			expectedOut: Error{
+				StatusCode:  1,
+				ProblemType: "urn:error",
+				Detail:      "it's an error",
+				Subproblems: []Subproblem{
+					{
+						Type:       "urn:error:sub",
+						Detail:     "it's a subproblem",
+						Identifier: &AuthzID{Type: "dns", Value: "example"},
+					},
+				},
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		out := tc.wire.error(nil)
+		if !reflect.DeepEqual(*out, tc.expectedOut) {
+			t.Errorf("Unexpected error: wanted %v, got %v", tc.expectedOut, *out)
+		}
+	}
+}
+
+func TestErrorStringerWithSubproblems(t *testing.T) {
+	err := Error{
+		StatusCode:  1,
+		ProblemType: "urn:error",
+		Detail:      "it's an error",
+		Subproblems: []Subproblem{
+			{
+				Type:   "urn:error:sub",
+				Detail: "it's a subproblem",
+			},
+			{
+				Type:       "urn:error:sub",
+				Detail:     "it's a subproblem",
+				Identifier: &AuthzID{Type: "dns", Value: "example"},
+			},
+		},
+	}
+	expectedStr := "1 urn:error: it's an error; subproblems:\n\turn:error:sub: it's a subproblem\n\turn:error:sub: [dns: example] it's a subproblem"
+	if err.Error() != expectedStr {
+		t.Errorf("Unexpected error string: wanted %q, got %q", expectedStr, err.Error())
+	}
+}