diff --git a/tsdb/chunkenc/float_histogram_st.go b/tsdb/chunkenc/float_histogram_st.go
index 90ef55290a..98f349d8d9 100644
--- a/tsdb/chunkenc/float_histogram_st.go
+++ b/tsdb/chunkenc/float_histogram_st.go
@@ -139,7 +139,7 @@ func (c *FloatHistogramSTChunk) Appender() (Appender, error) {
 			st:              it.st,
 			stDiff:          it.stDiff,
 			firstSTKnown:    it.firstSTKnown,
-			firstSTChangeOn: uint16(it.firstSTChangeOn),
+			firstSTChangeOn: it.firstSTChangeOn,
 		},
 	}
 	return a, nil
@@ -409,7 +409,13 @@ func (*FloatHistogramSTAppender) AppendHistogram(*HistogramAppender, int64, int6
 
 // AppendFloatHistogram implements Appender for FloatHistogramSTAppender.
 func (a *FloatHistogramSTAppender) AppendFloatHistogram(prev *FloatHistogramAppender, st, t int64, fh *histogram.FloatHistogram, appendOnly bool) (Chunk, bool, Appender, error) {
-	if a.NumSamples() == 0 {
+	numSamples := a.NumSamples()
+
+	if numSamples == int(a.sampleCountMask()) {
+		panic("chunk capacity exceeded")
+	}
+
+	if numSamples == 0 {
 		a.appendFloatHistogramST(st, t, fh)
 		if fh.CounterResetHint == histogram.GaugeType {
 			a.setCounterResetHeader(GaugeType)
diff --git a/tsdb/chunkenc/float_histogram_st_test.go b/tsdb/chunkenc/float_histogram_st_test.go
index dccfea4e75..6e64010994 100644
--- a/tsdb/chunkenc/float_histogram_st_test.go
+++ b/tsdb/chunkenc/float_histogram_st_test.go
@@ -577,3 +577,7 @@ func TestFloatHistogramSTAppenderPreviousEmbeddedAppenderUsesSTHeader(t *testing
 	require.NoError(t, err)
 	require.Equal(t, CounterReset, nextChunk.GetCounterResetHeader())
 }
+
+func TestFloatHistogramSTChunkOverFlowPanics(t *testing.T) {
+	testChunkOverFlowPanics(t, EncFloatHistogramST, ValFloatHistogram)
+}
diff --git a/tsdb/chunkenc/histogram_st.go b/tsdb/chunkenc/histogram_st.go
index fec4463340..5b1226224d 100644
--- a/tsdb/chunkenc/histogram_st.go
+++ b/tsdb/chunkenc/histogram_st.go
@@ -127,7 +127,7 @@ func (c *HistogramSTChunk) Appender() (Appender, error) {
 			st:              it.st,
 			stDiff:          it.stDiff,
 			firstSTKnown:    it.firstSTKnown,
-			firstSTChangeOn: uint16(it.firstSTChangeOn),
+			firstSTChangeOn: it.firstSTChangeOn,
 		},
 	}
 	return a, nil
@@ -412,7 +412,13 @@ func (*HistogramSTAppender) AppendFloatHistogram(*FloatHistogramAppender, int64,
 
 // AppendHistogram implements Appender for HistogramSTAppender.
 func (a *HistogramSTAppender) AppendHistogram(prev *HistogramAppender, st, t int64, h *histogram.Histogram, appendOnly bool) (Chunk, bool, Appender, error) {
-	if a.NumSamples() == 0 {
+	numSamples := a.NumSamples()
+
+	if numSamples == int(a.sampleCountMask()) {
+		panic("chunk capacity exceeded")
+	}
+
+	if numSamples == 0 {
 		a.appendHistogramST(st, t, h)
 		if h.CounterResetHint == histogram.GaugeType {
 			a.setCounterResetHeader(GaugeType)
diff --git a/tsdb/chunkenc/histogram_st_test.go b/tsdb/chunkenc/histogram_st_test.go
index f5b3d3eeb6..4462a5f0f0 100644
--- a/tsdb/chunkenc/histogram_st_test.go
+++ b/tsdb/chunkenc/histogram_st_test.go
@@ -574,3 +574,7 @@ func TestHistogramSTAppenderPreviousEmbeddedAppenderUsesSTHeader(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, CounterReset, nextChunk.GetCounterResetHeader())
 }
+
+func TestHistogramSTChunkOverFlowPanics(t *testing.T) {
+	testChunkOverFlowPanics(t, EncHistogramST, ValHistogram)
+}
diff --git a/tsdb/chunkenc/st.go b/tsdb/chunkenc/st.go
index 2bfb2d7353..026f523e17 100644
--- a/tsdb/chunkenc/st.go
+++ b/tsdb/chunkenc/st.go
@@ -21,7 +21,7 @@ const (
 
 type stEncoder struct {
 	st, stDiff      int64
-	firstSTChangeOn uint16
+	firstSTChangeOn uint8
 	firstSTKnown    bool
 }
 
@@ -48,18 +48,7 @@ func writeHeaderFirstSTChangeOn(b []byte, firstSTChangeOn uint16) {
 }
 
 func readSTHeader(b []byte) (firstSTKnown bool, firstSTChangeOn uint8) {
-	if b[0] == 0x00 {
-		return false, 0
-	}
-	if b[0] == 0x80 {
-		return true, 0
-	}
-	mask := byte(0x80)
-	if b[0]&mask != 0 {
-		firstSTKnown = true
-	}
-	mask = 0x7F
-	return firstSTKnown, b[0] & mask
+	return b[0]&0x80 != 0, b[0] & 0x7F
 }
 
 // encode writes the start timestamp data for the current histogram or float histogram sample and updates the encoder state.
@@ -92,7 +81,7 @@ func (e *stEncoder) encode(b *bstream, num uint16, curT, prevT, st int64) {
 		if e.firstSTChangeOn == 0 {
 			if st != e.st || num-1 == maxFirstSTChangeOn {
 				stDiff := prevT - st
-				e.firstSTChangeOn = num - 1
+				e.firstSTChangeOn = uint8(num - 1)
 				writeHeaderFirstSTChangeOn(b.bytes()[histogramHeaderSize-1:], num-1)
 				putVarbitInt(b, stDiff)
 				e.stDiff = stDiff