diff --git a/CONFIG.md b/CONFIG.md
index 83ad933a..39dec2bd 100644
--- a/CONFIG.md
+++ b/CONFIG.md
@@ -117,7 +117,7 @@ Causes screen blanking during some IEC operations (currently only JiffyDOS file
 
 Adds support for DolphinDOS fast protocol to the IEC bus, using UserPort cable.
 
-Needs some space in KERNAL segment. If unsure - enable.
+Needs about 160 buytes in KERNAL segment. If unsure - enable.
 
 ### `CONFIG_IEC_DOLPHINDOS_FAST`
 
diff --git a/c64/aliases/,aliases_config.s b/c64/aliases/,aliases_config.s
index e9b6744e..c9a096d9 100644
--- a/c64/aliases/,aliases_config.s
+++ b/c64/aliases/,aliases_config.s
@@ -118,6 +118,14 @@
 	.error "CONFIG_RS232_UP9600 is not compatible with CONFIG_TAPE_*"
 #endif
 
+#if CONFIG_IEC_DOLPHINDOS && !CONFIG_IEC
+	.error "CONFIG_IEC_DOLPHINDOS requires CONFIG_IEC"
+#endif
+
+#if CONFIG_IEC_DOLPHINDOS_FAST && !CONFIG_IEC_DOLPHINDOS
+	.error "CONFIG_IEC_DOLPHINDOS_FAST requires CONFIG_IEC_DOLPHINDOS"
+#endif
+
 #if CONFIG_IEC_JIFFYDOS && !CONFIG_IEC
 	.error "CONFIG_IEC_JIFFYDOS requires CONFIG_IEC"
 #endif
diff --git a/c64/aliases/,aliases_ram_lowmem.s b/c64/aliases/,aliases_ram_lowmem.s
index 8f522b21..c554e0de 100644
--- a/c64/aliases/,aliases_ram_lowmem.s
+++ b/c64/aliases/,aliases_ram_lowmem.s
@@ -103,7 +103,7 @@
 	.label PTR1      = $9E  //          -- NOT IMPLEMENTED --
 	.label PTR2      = $9F  //          -- NOT IMPLEMENTED --
 	.label TIME      = $A0  // $A0-$A2  jiffy clock
-#if !CONFIG_IEC_JIFFYDOS	
+#if !CONFIG_IEC_JIFFYDOS && !CONFIG_IEC_DOLPHINDOS
 	.label TSFCNT    = $A3  //          temporary variable for tape and IEC, [!] our usage differs
 #else
 	.label IECPROTO  = $A3  //          -- WIP -- [!] 0 = normal, 1 = JiffyDOS, >= $80 for unknown