diff --git a/src/path/filepath/path_plan9.go b/src/path/filepath/path_plan9.go
index 60d46d9d42..ec792fc831 100644
--- a/src/path/filepath/path_plan9.go
+++ b/src/path/filepath/path_plan9.go
@@ -18,6 +18,9 @@ func volumeNameLen(path string) int {
 }
 
 // HasPrefix exists for historical compatibility and should not be used.
+//
+// Deprecated: HasPrefix does not respect path boundaries and
+// does not ignore case when required.
 func HasPrefix(p, prefix string) bool {
 	return strings.HasPrefix(p, prefix)
 }
diff --git a/src/path/filepath/path_unix.go b/src/path/filepath/path_unix.go
index dddcac0a5c..d77ff24cdc 100644
--- a/src/path/filepath/path_unix.go
+++ b/src/path/filepath/path_unix.go
@@ -21,7 +21,8 @@ func volumeNameLen(path string) int {
 
 // HasPrefix exists for historical compatibility and should not be used.
 //
-// Deprecated: Use strings.HasPrefix instead.
+// Deprecated: HasPrefix does not respect path boundaries and
+// does not ignore case when required.
 func HasPrefix(p, prefix string) bool {
 	return strings.HasPrefix(p, prefix)
 }
diff --git a/src/path/filepath/path_windows.go b/src/path/filepath/path_windows.go
index 359703de26..0d8b62015c 100644
--- a/src/path/filepath/path_windows.go
+++ b/src/path/filepath/path_windows.go
@@ -65,6 +65,9 @@ func volumeNameLen(path string) int {
 }
 
 // HasPrefix exists for historical compatibility and should not be used.
+//
+// Deprecated: HasPrefix does not respect path boundaries and
+// does not ignore case when required.
 func HasPrefix(p, prefix string) bool {
 	if strings.HasPrefix(p, prefix) {
 		return true