diff --git a/gui/default/syncthing/core/syncthingController.js b/gui/default/syncthing/core/syncthingController.js
index 6a77e514e..adca42026 100755
--- a/gui/default/syncthing/core/syncthingController.js
+++ b/gui/default/syncthing/core/syncthingController.js
@@ -3051,7 +3051,11 @@ angular.module('syncthing.core')
                 arch += " Container";
             }
 
-            return $scope.version.version + ', ' + os + ' (' + arch + ')';
+            var verStr = $scope.version.version;
+            if ($scope.version.extra) {
+                verStr += ' (' + $scope.version.extra + ')';
+            }
+            return verStr + ', ' + os + ' (' + arch + ')';
         };
 
         $scope.versionBase = function () {
diff --git a/lib/api/api.go b/lib/api/api.go
index 38b5d2c92..1d4116ef7 100644
--- a/lib/api/api.go
+++ b/lib/api/api.go
@@ -713,6 +713,7 @@ func (*service) getSystemVersion(w http.ResponseWriter, _ *http.Request) {
 		"version":     build.Version,
 		"codename":    build.Codename,
 		"longVersion": build.LongVersion,
+		"extra":       build.Extra,
 		"os":          runtime.GOOS,
 		"arch":        runtime.GOARCH,
 		"isBeta":      build.IsBeta,
diff --git a/lib/build/build.go b/lib/build/build.go
index 285cf65e7..a389ac146 100644
--- a/lib/build/build.go
+++ b/lib/build/build.go
@@ -35,6 +35,7 @@ var (
 	IsCandidate bool
 	IsBeta      bool
 	LongVersion string
+	Extra       string
 
 	allowedVersionExp = regexp.MustCompile(`^v\d+\.\d+\.\d+(-[a-z0-9]+)*(\.\d+)*(\+\d+-g[0-9a-f]+)?(-[^\s]+)?$`)
 
@@ -46,6 +47,8 @@ var (
 	}
 )
 
+const versionExtraAllowedChars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-. "
+
 func init() {
 	if Version != "unknown-dev" {
 		// If not a generic dev build, version string should come from git describe
@@ -75,6 +78,7 @@ func setBuildData() {
 	IsRelease = exp.MatchString(Version)
 	IsCandidate = strings.Contains(Version, "-rc.")
 	IsBeta = strings.Contains(Version, "-")
+	Extra = filterString(os.Getenv("STVERSIONEXTRA"), versionExtraAllowedChars)
 
 	stamp, _ := strconv.Atoi(Stamp)
 	Date = time.Unix(int64(stamp), 0)
@@ -103,7 +107,22 @@ func TagsList() []string {
 			tags = append(tags, strings.ToLower(envVar))
 		}
 	}
+	if Extra != "" {
+		tags = append(tags, Extra)
+	}
 
 	sort.Strings(tags)
 	return tags
 }
+
+// filterString returns a copy of s with all characters not in allowedChars
+// removed.
+func filterString(s, allowedChars string) string {
+	var res strings.Builder
+	for _, c := range s {
+		if strings.ContainsRune(allowedChars, c) {
+			res.WriteRune(c)
+		}
+	}
+	return res.String()
+}
diff --git a/lib/build/build_test.go b/lib/build/build_test.go
index 797611694..e2918c018 100644
--- a/lib/build/build_test.go
+++ b/lib/build/build_test.go
@@ -35,3 +35,23 @@ func TestAllowedVersions(t *testing.T) {
 		}
 	}
 }
+
+func TestFilterString(t *testing.T) {
+	cases := []struct {
+		input  string
+		filter string
+		output string
+	}{
+		{"abcba", "abc", "abcba"},
+		{"abcba", "ab", "abba"},
+		{"abcba", "c", "c"},
+		{"abcba", "!", ""},
+		{"Foo (v1.5)", versionExtraAllowedChars, "Foo v1.5"},
+	}
+
+	for i, c := range cases {
+		if out := filterString(c.input, c.filter); out != c.output {
+			t.Errorf("%d: %q != %q", i, out, c.output)
+		}
+	}
+}