diff --git a/Source/HBIOS/cvdu.asm b/Source/HBIOS/cvdu.asm
index 96272b4f..4b51dfa2 100644
--- a/Source/HBIOS/cvdu.asm
+++ b/Source/HBIOS/cvdu.asm
@@ -96,6 +96,7 @@ CVDU_FNTBL:
 	.DW	KBD_READ
 #IF (($ - CVDU_FNTBL) != (VDA_FNCNT * 2))
 	.ECHO	"*** INVALID CVDU FUNCTION TABLE ***\n"
+	FAIL
 #ENDIF
 
 CVDU_VDAINI:
diff --git a/Source/HBIOS/tms.asm b/Source/HBIOS/tms.asm
index 4759cf61..832e99e0 100644
--- a/Source/HBIOS/tms.asm
+++ b/Source/HBIOS/tms.asm
@@ -136,6 +136,7 @@ TMS_FNTBL:
 #ENDIF
 #IF (($ - TMS_FNTBL) != (VDA_FNCNT * 2))
 	.ECHO	"*** INVALID TMS FUNCTION TABLE ***\n"
+	FAIL
 #ENDIF
 
 TMS_VDAINI:
diff --git a/Source/HBIOS/vdu.asm b/Source/HBIOS/vdu.asm
index b8cbec60..1c2a2ca1 100644
--- a/Source/HBIOS/vdu.asm
+++ b/Source/HBIOS/vdu.asm
@@ -150,6 +150,7 @@ VDU_FNTBL:
 	.DW	PPK_READ
 #IF (($ - VDU_FNTBL) != (VDA_FNCNT * 2))
 	.ECHO	"*** INVALID VDU FUNCTION TABLE ***\n"
+	FAIL
 #ENDIF
 
 VDU_VDAINI:
diff --git a/Source/HBIOS/vga.asm b/Source/HBIOS/vga.asm
index 8bbd8d85..dde15dae 100644
--- a/Source/HBIOS/vga.asm
+++ b/Source/HBIOS/vga.asm
@@ -163,6 +163,7 @@ VGA_FNTBL:
 	.DW	KBD_READ
 #IF (($ - VGA_FNTBL) != (VDA_FNCNT * 2))
 	.ECHO	"*** INVALID VGA FUNCTION TABLE ***\n"
+	FAIL
 #ENDIF
 
 VGA_VDAINI: