diff --git a/Makefile b/Makefile
index 5c989128..e6c07c50 100644
--- a/Makefile
+++ b/Makefile
@@ -11,9 +11,14 @@ CP ?= cp
 
 CFLAGS_OPTIMIZATION ?= -O3
 
-O_DEBUG := 0
+O_DEBUG := 0  # debug binary
 O_NORL := 0  # no readline support
+O_PCRE := 0  # link with PCRE library
 O_NOLOC := 0  # no locale support
+O_NOMOUSE := 0  # no mouse support
+O_NOBATCH := 0  # no built-in batch renamer
+O_NOFIFO := 0  # no FIFO previewer support
+O_CTX8 := 0  # enable 8 contexts
 
 # convert targets to flags for backwards compatibility
 ifneq ($(filter debug,$(MAKECMDGOALS)),)
diff --git a/misc/haiku/Makefile b/misc/haiku/Makefile
index 430b3d49..35480d35 100644
--- a/misc/haiku/Makefile
+++ b/misc/haiku/Makefile
@@ -9,9 +9,14 @@ CP ?= cp
 
 CFLAGS_OPTIMIZATION ?= -O3
 
-O_DEBUG := 0
+O_DEBUG := 0  # debug binary
 O_NORL := 0  # no readline support
+O_PCRE := 0  # link with PCRE library
 O_NOLOC := 0  # no locale support
+O_NOMOUSE := 0  # no mouse support
+O_NOBATCH := 0  # no built-in batch renamer
+O_NOFIFO := 0  # no FIFO previewer support
+O_CTX8 := 0  # enable 8 contexts
 
 # convert targets to flags for backwards compatibility
 ifneq ($(filter debug,$(MAKECMDGOALS)),)