diff --git a/pkg/sentry/kernel/syscalls.go b/pkg/sentry/kernel/syscalls.go
index 5d99d5ab3..fdf8b1c67 100644
--- a/pkg/sentry/kernel/syscalls.go
+++ b/pkg/sentry/kernel/syscalls.go
@@ -16,6 +16,7 @@ package kernel
 
 import (
 	"fmt"
+	"strconv"
 
 	"google.golang.org/protobuf/proto"
 	"gvisor.dev/gvisor/pkg/abi"
@@ -390,8 +391,13 @@ func RegisterSyscallTable(s *SyscallTable) {
 	}
 	allSyscallTables = append(allSyscallTables, s)
 	unimplementedSyscallCounterInit.Do(func() {
-		allowedValues := make([]string, 1)
-		// TODO(b/278108862): Add all other syscall numbers once doing so is possible.
+		allowedValues := make([]string, maxSyscallNum+2)
+		unimplementedSyscallNumbers = make(map[uintptr]string, len(allowedValues))
+		for i := uintptr(0); i <= maxSyscallNum; i++ {
+			s := strconv.Itoa(int(i))
+			allowedValues[i] = s
+			unimplementedSyscallNumbers[i] = s
+		}
 		allowedValues[len(allowedValues)-1] = outOfRangeSyscallNumber
 		unimplementedSyscallCounter = metric.MustCreateNewUint64Metric("unimplemented_syscalls", true, "Number of times the application tried to call an unimplemented syscall, broken down by syscall number", metric.NewField("sysno", allowedValues))
 	})
@@ -493,6 +499,9 @@ type SyscallInfo struct {
 //
 //go:nosplit
 func IncrementUnimplementedSyscallCounter(sysno uintptr) {
-	// TODO(b/278108862): Use the real syscall number once doing so is possible.s, found := unimplementedSyscallNumbers[sysno]
-	unimplementedSyscallCounter.Increment(outOfRangeSyscallNumber)
+	s, found := unimplementedSyscallNumbers[sysno]
+	if !found {
+		s = outOfRangeSyscallNumber
+	}
+	unimplementedSyscallCounter.Increment(s)
 }
diff --git a/runsc/container/metric_server_test.go b/runsc/container/metric_server_test.go
index fa4bb3946..1b954014b 100644
--- a/runsc/container/metric_server_test.go
+++ b/runsc/container/metric_server_test.go
@@ -859,29 +859,26 @@ func TestMetricServerDoesNotExportZeroValueCounters(t *testing.T) {
 
 	for _, test := range []struct {
 		cont          *Container
-		sysno         int
+		sysno         uintptr
 		wantExistence bool
 	}{
 		{unimpl1, 1337, true},
-		// TODO(b/278108862): Uncomment this: {unimpl1, 1338, false},
-		// TODO(b/278108862): Uncomment this: {unimpl2, 1337, false},
+		{unimpl1, 1338, false},
+		{unimpl2, 1337, false},
 		{unimpl2, 1338, true},
 	} {
-		// TODO(b/278108862): Undo this hack:
-		test.sysno = -1
-
 		t.Run(fmt.Sprintf("container %s syscall %d", test.cont.ID, test.sysno), func(t *testing.T) {
 			check := func() error {
 				got, _, err := metricDataPtr.GetPrometheusContainerInteger(metricclient.WantMetric{
 					Metric:      "testmetric_unimplemented_syscalls",
 					Sandbox:     test.cont.sandboxID(),
-					ExtraLabels: map[string]string{"sysno": strconv.Itoa(test.sysno)},
+					ExtraLabels: map[string]string{"sysno": strconv.Itoa(int(test.sysno))},
 				})
 				if test.wantExistence {
 					if err != nil {
 						return fmt.Errorf("cannot get unimplemented syscall metric for sysno=%d even though we expected its presence: %v", test.sysno, err)
 					}
-					if got <= 0 /* TODO(b/278108862): Revert to got != 1 */ {
+					if got != 1 {
 						return fmt.Errorf("expected counter value for unimplemented syscall %d be exactly 1, got %d", test.sysno, got)
 					}
 				} else /* !test.wantExistence */ {