diff --git a/doc/pprof.md b/doc/pprof.md
index 61dc29a2e..65986acf3 100644
--- a/doc/pprof.md
+++ b/doc/pprof.md
@@ -249,10 +249,10 @@ profile to be subtracted. This may result in some report entries having negative
 values.  Percentages in the report are relative to the total of 
 the diff base. 
 
-If the merged profile is output as a protocol buffer, all samples in 
-the diff base profile will have a label with the key "base" and a value of "1".
-If pprof is then used to look at the merged profile, it will behave as if 
-separate source and base profiles were passed in. 
+If the merged profile is output as a protocol buffer, all samples in
+the diff base profile will have a label with the key "pprof::base" and a value
+of "true". If pprof is then used to look at the merged profile, it will behave
+as if separate source and base profiles were passed in.
 
 The **-base** option can be used in the place of the **-diff_base** option, and
 may be preferrable when comparing two cumulative profiles, for example two
diff --git a/internal/driver/fetch.go b/internal/driver/fetch.go
index 5c9180f39..61d6af798 100644
--- a/internal/driver/fetch.go
+++ b/internal/driver/fetch.go
@@ -136,7 +136,7 @@ func grabSourcesAndBases(sources, bases []profileSource, isDiffBase bool, fetch
 		defer wg.Done()
 		pbase, mbase, savebase, countbase, errbase = chunkedGrab(bases, fetch, obj, ui)
 		if pbase != nil && isDiffBase {
-			pbase.SetTag("base", []string{"1"})
+			pbase.SetTag("pprof::base", []string{"true"})
 		}
 	}()
 	wg.Wait()
diff --git a/internal/driver/fetch_test.go b/internal/driver/fetch_test.go
index 5f4198d68..2ee472ca0 100644
--- a/internal/driver/fetch_test.go
+++ b/internal/driver/fetch_test.go
@@ -398,27 +398,27 @@ func TestFetchWithBase(t *testing.T) {
 				},
 				{
 					values: []int64{-2700, -608881724},
-					labels: map[string][]string{"base": {"1"}},
+					labels: map[string][]string{"pprof::base": {"true"}},
 				},
 				{
 					values: []int64{-100, -23992},
-					labels: map[string][]string{"base": {"1"}},
+					labels: map[string][]string{"pprof::base": {"true"}},
 				},
 				{
 					values: []int64{-200, -179943},
-					labels: map[string][]string{"base": {"1"}},
+					labels: map[string][]string{"pprof::base": {"true"}},
 				},
 				{
 					values: []int64{-100, -17778444},
-					labels: map[string][]string{"base": {"1"}},
+					labels: map[string][]string{"pprof::base": {"true"}},
 				},
 				{
 					values: []int64{-100, -75976},
-					labels: map[string][]string{"base": {"1"}},
+					labels: map[string][]string{"pprof::base": {"true"}},
 				},
 				{
 					values: []int64{-300, -63568134},
-					labels: map[string][]string{"base": {"1"}},
+					labels: map[string][]string{"pprof::base": {"true"}},
 				},
 			},
 			"",
diff --git a/internal/report/report.go b/internal/report/report.go
index 1515021c3..4c6c99bc2 100644
--- a/internal/report/report.go
+++ b/internal/report/report.go
@@ -266,7 +266,7 @@ func (rpt *Report) newGraph(nodes graph.NodeSet) *graph.Graph {
 
 	// Remove tag marking samples from the base profiles, so it does not appear
 	// as a nodelet in the graph view.
-	prof.SetTag("base", []string{})
+	prof.SetTag("pprof::base", []string{})
 
 	formatTag := func(v int64, key string) string {
 		return measurement.ScaledLabel(v, key, o.OutputUnit)
@@ -1217,7 +1217,7 @@ func NewDefault(prof *profile.Profile, options Options) *Report {
 }
 
 // computeTotal computes the sum of the absolute value of all sample values.
-// If any samples have the tag "base" with value "1", then the total
+// If any samples have the tag "pprof::base" with value "true", then the total
 // will only include samples with that tag.
 func computeTotal(prof *profile.Profile, value, meanDiv func(v []int64) int64) int64 {
 	var div, total, diffDiv, diffTotal int64
@@ -1231,7 +1231,7 @@ func computeTotal(prof *profile.Profile, value, meanDiv func(v []int64) int64) i
 			v = -v
 		}
 		total += v
-		if sample.HasTag("base", "1") {
+		if sample.HasTag("pprof::base", "true") {
 			diffTotal += v
 			diffDiv += d
 		}
diff --git a/internal/report/report_test.go b/internal/report/report_test.go
index 8e689aef1..57e0bd266 100644
--- a/internal/report/report_test.go
+++ b/internal/report/report_test.go
@@ -330,7 +330,7 @@ func TestComputeTotal(t *testing.T) {
 		{
 			Location: []*profile.Location{testL[2], testL[1], testL[0]},
 			Value:    []int64{-10, 3},
-			Label:    map[string][]string{"base": {"1"}},
+			Label:    map[string][]string{"pprof::base": {"true"}},
 		},
 		{
 			Location: []*profile.Location{testL[2], testL[1], testL[0]},
@@ -339,12 +339,12 @@ func TestComputeTotal(t *testing.T) {
 		{
 			Location: []*profile.Location{testL[2], testL[1], testL[0]},
 			Value:    []int64{-9000, 3},
-			Label:    map[string][]string{"base": {"1"}},
+			Label:    map[string][]string{"pprof::base": {"true"}},
 		},
 		{
 			Location: []*profile.Location{testL[2], testL[1], testL[0]},
 			Value:    []int64{-1, 3},
-			Label:    map[string][]string{"base": {"1"}},
+			Label:    map[string][]string{"pprof::base": {"true"}},
 		},
 		{
 			Location: []*profile.Location{testL[4], testL[2], testL[0]},
@@ -353,7 +353,7 @@ func TestComputeTotal(t *testing.T) {
 		{
 			Location: []*profile.Location{testL[2], testL[1], testL[0]},
 			Value:    []int64{100, 3},
-			Label:    map[string][]string{"base": {"1"}},
+			Label:    map[string][]string{"pprof::base": {"true"}},
 		},
 	}