diff --git a/cmd/zoekt-sourcegraph-indexserver/main.go b/cmd/zoekt-sourcegraph-indexserver/main.go
index aff3d2c95..c1ac19f5b 100644
--- a/cmd/zoekt-sourcegraph-indexserver/main.go
+++ b/cmd/zoekt-sourcegraph-indexserver/main.go
@@ -1213,7 +1213,7 @@ func (rc *rootConfig) registerRootFlags(fs *flag.FlagSet) {
 	fs.IntVar(&rc.blockProfileRate, "block_profile_rate", getEnvWithDefaultInt("BLOCK_PROFILE_RATE", -1), "Sampling rate of Go's block profiler in nanoseconds. Values <=0 disable the blocking profiler Var(default). A value of 1 includes every blocking event. See https://pkg.go.dev/runtime#SetBlockProfileRate")
 	fs.DurationVar(&rc.backoffDuration, "backoff_duration", getEnvWithDefaultDuration("BACKOFF_DURATION", 10*time.Minute), "for the given duration we backoff from enqueue operations for a repository that's failed its previous indexing attempt. Consecutive failures increase the duration of the delay linearly up to the maxBackoffDuration. A negative value disables indexing backoff.")
 	fs.DurationVar(&rc.maxBackoffDuration, "max_backoff_duration", getEnvWithDefaultDuration("MAX_BACKOFF_DURATION", 120*time.Minute), "the maximum duration to backoff from enqueueing a repo for indexing.  A negative value disables indexing backoff.")
-	fs.BoolVar(&rc.useGRPC, "use_grpc", getEnvWithDefaultBool("GRPC_ENABLED", false), "use the gRPC API to talk to Sourcegraph")
+	fs.BoolVar(&rc.useGRPC, "use_grpc", mustGetBoolFromEnvironmentVariables([]string{"GRPC_ENABLED", "SG_FEATURE_FLAG_GRPC"}, true), "use the gRPC API to talk to Sourcegraph")
 
 	// flags related to shard merging
 	fs.DurationVar(&rc.vacuumInterval, "vacuum_interval", getEnvWithDefaultDuration("SRC_VACUUM_INTERVAL", 24*time.Hour), "run vacuum this often")
@@ -1596,3 +1596,36 @@ func main() {
 		log.Fatal(err)
 	}
 }
+
+// mustGetBoolFromEnvironmentVariables is like getBoolFromEnvironmentVariables, but it panics
+// if any of the provided environment variables fails to parse as a boolean.
+func mustGetBoolFromEnvironmentVariables(envVarNames []string, defaultBool bool) bool {
+	value, err := getBoolFromEnvironmentVariables(envVarNames, defaultBool)
+	if err != nil {
+		panic(err)
+	}
+
+	return value
+}
+
+// getBoolFromEnvironmentVariables returns the boolean defined by the first environment
+// variable listed in envVarNames that is set in the current process environment, or the defaultBool if none are set.
+//
+// An error is returned of the provided environment variables fails to parse as a boolean.
+func getBoolFromEnvironmentVariables(envVarNames []string, defaultBool bool) (bool, error) {
+	for _, envVar := range envVarNames {
+		v := os.Getenv(envVar)
+		if v == "" {
+			continue
+		}
+
+		b, err := strconv.ParseBool(v)
+		if err != nil {
+			return false, fmt.Errorf("parsing environment variable %q to boolean: %v", envVar, err)
+		}
+
+		return b, nil
+	}
+
+	return defaultBool, nil
+}
diff --git a/cmd/zoekt-sourcegraph-indexserver/main_test.go b/cmd/zoekt-sourcegraph-indexserver/main_test.go
index 6981601ac..0d3f65cd3 100644
--- a/cmd/zoekt-sourcegraph-indexserver/main_test.go
+++ b/cmd/zoekt-sourcegraph-indexserver/main_test.go
@@ -286,6 +286,103 @@ func TestDefaultGRPCServiceConfigurationSyntax(t *testing.T) {
 	}
 }
 
+func TestGetBoolFromEnvironmentVariables(t *testing.T) {
+	testCases := []struct {
+		name         string
+		envVarsToSet map[string]string
+
+		envVarNames []string
+		defaultBool bool
+
+		wantBool bool
+		wantErr  bool
+	}{
+		{
+			name: "respect default value: true",
+
+			envVarsToSet: map[string]string{},
+
+			envVarNames: []string{"FOO", "BAR"},
+			defaultBool: true,
+
+			wantBool: true,
+		},
+		{
+			name: "respect default value: false",
+
+			envVarsToSet: map[string]string{},
+
+			envVarNames: []string{"FOO", "BAR"},
+			defaultBool: false,
+
+			wantBool: false,
+		},
+		{
+			name: "read from environment",
+
+			envVarsToSet: map[string]string{"FOO": "1"},
+
+			envVarNames: []string{"FOO"},
+			defaultBool: false,
+
+			wantBool: true,
+		},
+		{
+			name: "read from first env var that is set",
+
+			envVarsToSet: map[string]string{
+				"BAR": "false",
+				"BAZ": "true",
+			},
+
+			envVarNames: []string{"FOO", "BAR", "BAZ"},
+			defaultBool: true,
+
+			wantBool: false,
+		},
+
+		{
+			name: "should error for invalid input",
+
+			envVarsToSet: map[string]string{"INVALID": "not a boolean"},
+
+			envVarNames: []string{"INVALID"},
+			defaultBool: false,
+
+			wantErr: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run("", func(t *testing.T) {
+			// Prepare the environment by loading all the appropriate environment variables
+			for _, v := range tc.envVarNames {
+				_ = os.Unsetenv(v)
+			}
+
+			for k, _ := range tc.envVarsToSet {
+				_ = os.Unsetenv(k)
+			}
+
+			for k, v := range tc.envVarsToSet {
+				t.Setenv(k, v)
+			}
+
+			// Run the test
+			got, err := getBoolFromEnvironmentVariables(tc.envVarNames, tc.defaultBool)
+
+			// Examine the results
+			if tc.wantErr != (err != nil) {
+				t.Fatalf("unexpected error (wantErr = %t): %v", tc.wantErr, err)
+			}
+
+			if got != tc.wantBool {
+				t.Errorf("got %v, want %v", got, tc.wantBool)
+			}
+		})
+	}
+}
+
 func TestAddDefaultPort(t *testing.T) {
 	tests := []struct {
 		name  string