diff --git a/internal/toml-test/tests/valid/table/sub-sub-subtable.json b/internal/toml-test/tests/valid/table/sub-sub-subtable.json
new file mode 100644
index 00000000..eaafc8cc
--- /dev/null
+++ b/internal/toml-test/tests/valid/table/sub-sub-subtable.json
@@ -0,0 +1,16 @@
+{
+    "x": {
+        "y": {
+            "z": {
+                "a": {
+                    "type": "integer",
+                    "value": "1"
+                },
+                "b": {
+                    "type": "integer",
+                    "value": "2"
+                }
+            }
+        }
+    }
+}
diff --git a/internal/toml-test/tests/valid/table/sub-sub-subtable.toml b/internal/toml-test/tests/valid/table/sub-sub-subtable.toml
new file mode 100644
index 00000000..dc8d7015
--- /dev/null
+++ b/internal/toml-test/tests/valid/table/sub-sub-subtable.toml
@@ -0,0 +1,3 @@
+[x.y.z]
+a = 1
+b = 2
diff --git a/parse.go b/parse.go
index 3f2c090c..385a7c05 100644
--- a/parse.go
+++ b/parse.go
@@ -442,7 +442,7 @@ func (p *parser) valueInlineTable(it item, parentIsArray bool) (any, tomlType) {
 		outerKey     = p.currentKey
 	)
 
-	p.context = append(p.context, p.currentKey)
+	p.context = p.context.add(p.currentKey)
 	prevContext := p.context
 	p.currentKey = ""
 
@@ -603,7 +603,7 @@ func (p *parser) addContext(key Key, array bool) {
 	} else {
 		p.setValue(key.last(), make(map[string]any))
 	}
-	p.context = append(p.context, key.last())
+	p.context = p.context.add(key.last())
 }
 
 // setValue sets the given key to the given value in the current context.
@@ -614,10 +614,10 @@ func (p *parser) setValue(key string, value any) {
 		tmpHash    any
 		ok         bool
 		hash       = p.mapping
-		keyContext = make(Key, 0, len(p.context)+1)
+		keyContext = make(Key, len(p.context)+1)
 	)
-	for _, k := range p.context {
-		keyContext = append(keyContext, k)
+	for i, k := range p.context {
+		keyContext[i] = k
 		if tmpHash, ok = hash[k]; !ok {
 			p.bug("Context for key '%s' has not been established.", keyContext)
 		}
@@ -632,7 +632,7 @@ func (p *parser) setValue(key string, value any) {
 			p.panicf("Key '%s' has already been defined.", keyContext)
 		}
 	}
-	keyContext = append(keyContext, key)
+	keyContext[len(p.context)] = key
 
 	if _, ok := hash[key]; ok {
 		// Normally redefining keys isn't allowed, but the key could have been
@@ -667,8 +667,8 @@ func (p *parser) setValue(key string, value any) {
 // Note that if `key` is empty, then the type given will be applied to the
 // current context (which is either a table or an array of tables).
 func (p *parser) setType(key string, typ tomlType, pos Position) {
-	keyContext := make(Key, 0, len(p.context)+1)
-	keyContext = append(keyContext, p.context...)
+	keyContext := make(Key, len(p.context), len(p.context)+1)
+	copy(keyContext, p.context)
 	if len(key) > 0 { // allow type setting for hashes
 		keyContext = append(keyContext, key)
 	}