Index: Mk/bsd.options.mk
===================================================================
--- Mk/bsd.options.mk
+++ Mk/bsd.options.mk
@@ -263,7 +263,11 @@
 
 # Remove options the port maintainer doesn't want, part 2
 .for opt in ${_ALL_EXCLUDE:O:u}
+.  if !empty(COMPLETE_OPTIONS_LIST:M${opt})
 PORT_OPTIONS:=		${PORT_OPTIONS:N${opt}}
+.  else
+DEV_WARNING+=	"One of OPTIONS_EXCLUDE* contains ${opt} but it is not a valid option for this port"
+.  endif
 .endfor
 
 ## Now create the list of activated options
@@ -297,13 +301,19 @@
 .    if !empty(COMPLETE_OPTIONS_LIST:M${opt})
 PORT_OPTIONS+=	${opt}
 NEW_OPTIONS:=	${NEW_OPTIONS:N${opt}}
+.    else
+WARNING+=	"${OPTIONS_NAME}_SET contains ${opt} but it is not a valid option for this port"
 .    endif
 .  endfor
 
 ## Unset the options excluded per-port (set by user in make.conf)
 .  for opt in ${${OPTIONS_NAME}_UNSET}
+.    if !empty(COMPLETE_OPTIONS_LIST:M${opt})
 PORT_OPTIONS:=	${PORT_OPTIONS:N${opt}}
 NEW_OPTIONS:=	${NEW_OPTIONS:N${opt}}
+.    else
+WARNING+=	"${OPTIONS_NAME}_UNSET contains ${opt} but it is not a valid option for this port"
+.    endif
 .  endfor
 
 ## options files (from dialog)
@@ -325,12 +335,18 @@
 .    if !empty(COMPLETE_OPTIONS_LIST:M${opt})
 PORT_OPTIONS+=	${opt}
 NEW_OPTIONS:=	${NEW_OPTIONS:N${opt}}
+.    else
+WARNING+=	"The options file contains ${opt} but it is not a valid option for this port, maybe re-run make config"
 .    endif
 .  endfor
 
 .for opt in ${OPTIONS_FILE_UNSET}
+.    if !empty(COMPLETE_OPTIONS_LIST:M${opt})
 PORT_OPTIONS:=	${PORT_OPTIONS:N${opt}}
 NEW_OPTIONS:=	${NEW_OPTIONS:N${opt}}
+.    else
+WARNING+=	"The options file contains ${opt} but it is not a valid option for this port, maybe re-run make config"
+.    endif
 .endfor
 
 .endif
@@ -355,13 +371,19 @@
 .    if !empty(COMPLETE_OPTIONS_LIST:M${opt})
 PORT_OPTIONS+=	${opt}
 NEW_OPTIONS:=	${NEW_OPTIONS:N${opt}}
+.    else
+WARNING+=	"${OPTIONS_NAME}_FORCE_SET contains ${opt} but it is not a valid option for this port"
 .    endif
 .  endfor
 
 ## Unset the options excluded per-port (set by user in make.conf)
 .  for opt in ${${OPTIONS_NAME}_UNSET_FORCE}
+.    if !empty(COMPLETE_OPTIONS_LIST:M${opt})
 PORT_OPTIONS:=	${PORT_OPTIONS:N${opt}}
 NEW_OPTIONS:=	${NEW_OPTIONS:N${opt}}
+.    else
+WARNING+=	"${OPTIONS_NAME}_FORCE_UNSET contains ${opt} but it is not a valid option for this port"
+.    endif
 .  endfor
 
 
@@ -414,7 +436,13 @@
 .endfor
 
 # Finally, add options required by slave ports
-PORT_OPTIONS+=	${OPTIONS_SLAVE}
+.for opt in ${OPTIONS_SLAVE}
+.  if !empty(COMPLETE_OPTIONS_LIST:M${opt})
+PORT_OPTIONS+=	${opt}
+.  else
+DEV_WARNING+=	"OPTIONS_SLAVE contains ${opt} but it is not a valid option for this port"
+.  endif
+.endfor
 
 # Sort options and eliminate duplicates
 PORT_OPTIONS:=	${PORT_OPTIONS:O:u}
@@ -506,6 +534,17 @@
 .    for configure in CONFIGURE CMAKE MESON QMAKE
 .      if defined(${opt}_${configure}_ON)
 ${configure}_ARGS+=	${${opt}_${configure}_ON}
+.        if !defined(${opt}_${configure}_OFF)
+.          if ${configure:MCONFIGURE}
+DEV_WARNING+=	"You have ${opt}_${configure}_ON defined but ${opt}_${configure}_OFF is not, make sure the feature cannot be auto-activated, or maybe use ${opt}_${configure}_WITH or ${opt}_${configure}_ENABLE"
+.          elsif ${configure:MCMAKE}
+DEV_WARNING+=	"You have ${opt}_${configure}_ON defined but ${opt}_${configure}_OFF is not, make sure the feature cannot be auto-activated, or maybe use ${opt}_${configure}_BOOL or ${opt}_${configure}_BOOL_OFF"
+.          elsif ${configure:MMESON}
+DEV_WARNING+=	"You have ${opt}_${configure}_ON defined but ${opt}_${configure}_OFF is not, make sure the feature cannot be auto-activated, or maybe use ${opt}_${configure}_TRUE/FALSE/YES/NO"
+.          else
+DEV_WARNING+=	"You have ${opt}_${configure}_ON defined but ${opt}_${configure}_OFF is not, make sure the feature cannot be auto-activated"
+.          endif
+.        endif
 .      endif
 .    endfor
 .    for flags in ${_OPTIONS_FLAGS}
@@ -568,6 +607,17 @@
 .    for configure in CONFIGURE CMAKE MESON QMAKE
 .      if defined(${opt}_${configure}_OFF)
 ${configure}_ARGS+=	${${opt}_${configure}_OFF}
+.        if !defined(${opt}_${configure}_ON)
+.          if ${configure:MCONFIGURE}
+DEV_WARNING+=	"You have ${opt}_${configure}_OFF defined but ${opt}_${configure}_ON is not, make sure the feature cannot be auto-activated, or maybe use ${opt}_${configure}_WITH or ${opt}_${configure}_ENABLE"
+.          elsif ${configure:MCMAKE}
+DEV_WARNING+=	"You have ${opt}_${configure}_OFF defined but ${opt}_${configure}_ON is not, make sure the feature cannot be auto-activated, or maybe use ${opt}_${configure}_BOOL or ${opt}_${configure}_BOOL_OFF"
+.          elsif ${configure:MMESON}
+DEV_WARNING+=	"You have ${opt}_${configure}_OFF defined but ${opt}_${configure}_ON is not, make sure the feature cannot be auto-activated, or maybe use ${opt}_${configure}_TRUE/FALSE/YES/NO"
+.          else
+DEV_WARNING+=	"You have ${opt}_${configure}_OFF defined but ${opt}_${configure}_ON is not, make sure the feature cannot be auto-activated"
+.          endif
+.        endif
 .      endif
 .    endfor
 .    for flags in ${_OPTIONS_FLAGS}