diff --git a/internals/plan/extensions_test.go b/internals/plan/extensions_test.go
index 9885bf20..0be9d051 100644
--- a/internals/plan/extensions_test.go
+++ b/internals/plan/extensions_test.go
@@ -353,7 +353,7 @@ func (s *S) TestPlanExtensions(c *C) {
 	defer func() {
 		// Remove remaining registered extensions.
 		for _, field := range registeredExtensions {
-			plan.UnregisterExtension(field)
+			plan.UnregisterSectionExtension(field)
 		}
 	}()
 
@@ -363,7 +363,7 @@ nexttest:
 
 		// Unregister extensions from previous test iteraton.
 		for _, field := range registeredExtensions {
-			plan.UnregisterExtension(field)
+			plan.UnregisterSectionExtension(field)
 		}
 		registeredExtensions = []string{}
 
@@ -380,7 +380,7 @@ nexttest:
 						err = fmt.Errorf("%v", r)
 					}
 				}()
-				plan.RegisterExtension(e.field, e.ext)
+				plan.RegisterSectionExtension(e.field, e.ext)
 				registeredExtensions = append(registeredExtensions, e.field)
 				return nil
 			}()
@@ -430,11 +430,11 @@ nexttest:
 // registration and follows the built-in sections which are ordered
 // the same way they are defined in the Plan struct.
 func (s *S) TestSectionOrderExt(c *C) {
-	plan.RegisterExtension("x-field", &xExtension{})
-	plan.RegisterExtension("y-field", &yExtension{})
+	plan.RegisterSectionExtension("x-field", &xExtension{})
+	plan.RegisterSectionExtension("y-field", &yExtension{})
 	defer func() {
-		plan.UnregisterExtension("x-field")
-		plan.UnregisterExtension("y-field")
+		plan.UnregisterSectionExtension("x-field")
+		plan.UnregisterSectionExtension("y-field")
 	}()
 
 	layer, err := plan.ParseLayer(1, "label", reindent(`
diff --git a/internals/plan/plan.go b/internals/plan/plan.go
index 3d8dc663..d75146b7 100644
--- a/internals/plan/plan.go
+++ b/internals/plan/plan.go
@@ -81,11 +81,11 @@ var (
 // the YAML fields exposed in the Layer type, to catch inconsistencies.
 var builtinSections = []string{"summary", "description", "services", "checks", "log-targets"}
 
-// RegisterExtension adds a plan schema extension. All registrations must be
+// RegisterSectionExtension adds a plan schema extension. All registrations must be
 // done before the plan library is used. The order in which extensions are
 // registered determines the order in which the sections are marshalled.
 // Extension sections are marshalled after the built-in sections.
-func RegisterExtension(field string, ext SectionExtension) {
+func RegisterSectionExtension(field string, ext SectionExtension) {
 	if slices.Contains(builtinSections, field) {
 		panic(fmt.Sprintf("internal error: extension %q already used as built-in field", field))
 	}
@@ -96,9 +96,9 @@ func RegisterExtension(field string, ext SectionExtension) {
 	sectionExtensionsOrder = append(sectionExtensionsOrder, field)
 }
 
-// UnregisterExtension removes a plan schema extension. This is only
+// UnregisterSectionExtension removes a plan schema extension. This is only
 // intended for use by tests during cleanup.
-func UnregisterExtension(field string) {
+func UnregisterSectionExtension(field string) {
 	delete(sectionExtensions, field)
 	sectionExtensionsOrder = slices.DeleteFunc(sectionExtensionsOrder, func(n string) bool {
 		return n == field