diff --git a/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/filter_table.go b/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/filter_table.go
index c50cd1fd..9e3b7d6e 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/filter_table.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/filter_table.go
@@ -17,6 +17,8 @@ package accounts
 import (
 	"context"
 	"database/sql"
+
+	"github.com/matrix-org/gomatrixserverlib"
 )
 
 const filterSchema = `
@@ -38,12 +40,16 @@ CREATE INDEX IF NOT EXISTS account_filter_localpart ON account_filter(localpart)
 const selectFilterSQL = "" +
 	"SELECT filter FROM account_filter WHERE localpart = $1 AND id = $2"
 
+const selectFilterIDByContentSQL = "" +
+	"SELECT id FROM account_filter WHERE localpart = $1 AND filter = $2"
+
 const insertFilterSQL = "" +
 	"INSERT INTO account_filter (filter, id, localpart) VALUES ($1, DEFAULT, $2) RETURNING id"
 
 type filterStatements struct {
-	selectFilterStmt *sql.Stmt
-	insertFilterStmt *sql.Stmt
+	selectFilterStmt            *sql.Stmt
+	selectFilterIDByContentStmt *sql.Stmt
+	insertFilterStmt            *sql.Stmt
 }
 
 func (s *filterStatements) prepare(db *sql.DB) (err error) {
@@ -54,6 +60,9 @@ func (s *filterStatements) prepare(db *sql.DB) (err error) {
 	if s.selectFilterStmt, err = db.Prepare(selectFilterSQL); err != nil {
 		return
 	}
+	if s.selectFilterIDByContentStmt, err = db.Prepare(selectFilterIDByContentSQL); err != nil {
+		return
+	}
 	if s.insertFilterStmt, err = db.Prepare(insertFilterSQL); err != nil {
 		return
 	}
@@ -62,14 +71,37 @@ func (s *filterStatements) prepare(db *sql.DB) (err error) {
 
 func (s *filterStatements) selectFilter(
 	ctx context.Context, localpart string, filterID string,
-) (filter string, err error) {
+) (filter []byte, err error) {
 	err = s.selectFilterStmt.QueryRowContext(ctx, localpart, filterID).Scan(&filter)
 	return
 }
 
 func (s *filterStatements) insertFilter(
-	ctx context.Context, filter string, localpart string,
-) (pos string, err error) {
-	err = s.insertFilterStmt.QueryRowContext(ctx, filter, localpart).Scan(&pos)
+	ctx context.Context, filter []byte, localpart string,
+) (filterID string, err error) {
+	var existingFilterID string
+
+	// This can result in a race condition when two clients try to insert the
+	// same filter and localpart at the same time, however this is not a
+	// problem as both calls will result in the same filterID
+	filterJSON, err := gomatrixserverlib.CanonicalJSON(filter)
+	if err != nil {
+		return "", err
+	}
+
+	// Check if filter already exists in the database
+	err = s.selectFilterIDByContentStmt.QueryRowContext(ctx,
+		localpart, filterJSON).Scan(&existingFilterID)
+	if err != nil {
+		return "", err
+	}
+	// If it does, return the existing ID
+	if len(existingFilterID) != 0 {
+		return existingFilterID, err
+	}
+
+	// Otherwise insert the filter and return the new ID
+	err = s.insertFilterStmt.QueryRowContext(ctx, filterJSON, localpart).
+		Scan(&filterID)
 	return
 }
diff --git a/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/storage.go b/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/storage.go
index 33fbbd86..d5712eb5 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/storage.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/storage.go
@@ -321,22 +321,25 @@ func (d *Database) GetThreePIDsForLocalpart(
 }
 
 // GetFilter looks up the filter associated with a given local user and filter ID.
-// Returns an error if no such filter exists or if there was an error taling to the database.
+// Returns a filter represented as a byte slice. Otherwise returns an error if
+// no such filter exists or if there was an error talking to the database.
 func (d *Database) GetFilter(
 	ctx context.Context, localpart string, filterID string,
-) (string, error) {
+) ([]byte, error) {
 	return d.filter.selectFilter(ctx, localpart, filterID)
 }
 
 // PutFilter puts the passed filter into the database.
-// Returns an error if something goes wrong.
+// Returns the filterID as a string. Otherwise returns an error if something
+// goes wrong.
 func (d *Database) PutFilter(
-	ctx context.Context, localpart, filter string,
+	ctx context.Context, localpart string, filter []byte,
 ) (string, error) {
 	return d.filter.insertFilter(ctx, filter, localpart)
 }
 
-// CheckAccountAvailability checks if the username/localpart is already present in the database.
+// CheckAccountAvailability checks if the username/localpart is already present
+// in the database.
 // If the DB returns sql.ErrNoRows the Localpart isn't taken.
 func (d *Database) CheckAccountAvailability(ctx context.Context, localpart string) (bool, error) {
 	_, err := d.accounts.selectAccountByLocalpart(ctx, localpart)
diff --git a/src/github.com/matrix-org/dendrite/clientapi/routing/filter.go b/src/github.com/matrix-org/dendrite/clientapi/routing/filter.go
index 3c623147..4b84e293 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/routing/filter.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/routing/filter.go
@@ -60,7 +60,7 @@ func GetFilter(
 		}
 	}
 	filter := gomatrix.Filter{}
-	err = json.Unmarshal([]byte(res), &filter)
+	err = json.Unmarshal(res, &filter)
 	if err != nil {
 		httputil.LogThenError(req, err)
 	}
@@ -111,7 +111,7 @@ func PutFilter(
 		}
 	}
 
-	filterID, err := accountDB.PutFilter(req.Context(), localpart, string(filterArray))
+	filterID, err := accountDB.PutFilter(req.Context(), localpart, filterArray)
 	if err != nil {
 		return httputil.LogThenError(req, err)
 	}
diff --git a/src/github.com/matrix-org/dendrite/clientapi/routing/register.go b/src/github.com/matrix-org/dendrite/clientapi/routing/register.go
index 92c9b427..29e25764 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/routing/register.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/routing/register.go
@@ -28,7 +28,6 @@ import (
 
 	"github.com/matrix-org/dendrite/common/config"
 
-	log "github.com/sirupsen/logrus"
 	"github.com/matrix-org/dendrite/clientapi/auth"
 	"github.com/matrix-org/dendrite/clientapi/auth/authtypes"
 	"github.com/matrix-org/dendrite/clientapi/auth/storage/accounts"
@@ -37,6 +36,7 @@ import (
 	"github.com/matrix-org/dendrite/clientapi/jsonerror"
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
+	log "github.com/sirupsen/logrus"
 )
 
 const (