diff --git a/include/minix/com.h b/include/minix/com.h
index 443e50426..6fa517a93 100644
--- a/include/minix/com.h
+++ b/include/minix/com.h
@@ -398,12 +398,12 @@
 #define ALRM_TIME_LEFT  m2_l1	/* how many ticks were remaining */
 
 /* Field names for SYS_IRQCTL. */
-#define IRQ_REQUEST     m5_c1	/* what to do? */
+#define IRQ_REQUEST     m5_s1	/* what to do? */
 #  define IRQ_SETPOLICY     1	/* manage a slot of the IRQ table */
 #  define IRQ_RMPOLICY      2	/* remove a slot of the IRQ table */
 #  define IRQ_ENABLE        3	/* enable interrupts */
 #  define IRQ_DISABLE       4	/* disable interrupts */
-#define IRQ_VECTOR	m5_c2   /* irq vector */
+#define IRQ_VECTOR	m5_s2   /* irq vector */
 #define IRQ_POLICY	m5_i1   /* options for IRQCTL request */
 #  define IRQ_REENABLE  0x001	/* reenable IRQ line after interrupt */
 #  define IRQ_BYTE      0x100	/* byte values */      
@@ -425,10 +425,10 @@
 #define ABRT_MON_ADDR   m1_p1	/* virtual address of monitor params */
 
 /* Field names for _UMAP, _VIRCOPY, _PHYSCOPY. */
-#define CP_SRC_SPACE 	m5_c1	/* T or D space (stack is also D) */
+#define CP_SRC_SPACE 	m5_s1	/* T or D space (stack is also D) */
 #define CP_SRC_ENDPT	m5_i1	/* process to copy from */
 #define CP_SRC_ADDR	m5_l1	/* address where data come from */
-#define CP_DST_SPACE	m5_c2	/* T or D space (stack is also D) */
+#define CP_DST_SPACE	m5_s2	/* T or D space (stack is also D) */
 #define CP_DST_ENDPT	m5_i2	/* process to copy to */
 #define CP_DST_ADDR	m5_l2	/* address where data go to */
 #define CP_NR_BYTES	m5_l3	/* number of bytes to copy */
@@ -879,8 +879,8 @@
 #define VM_MMAP			(VM_RQ_BASE+10)
 #	define VMM_ADDR			m5_l1
 #	define VMM_LEN			m5_l2
-#	define VMM_PROT			m5_c1
-#	define VMM_FLAGS		m5_c2
+#	define VMM_PROT			m5_s1
+#	define VMM_FLAGS		m5_s2
 #	define VMM_FD			m5_i1
 #	define VMM_OFFSET		m5_i2
 #	define VMM_RETADDR		m5_l1	/* result */
diff --git a/include/minix/ipc.h b/include/minix/ipc.h
index 9bb459e91..58c7c8a8f 100644
--- a/include/minix/ipc.h
+++ b/include/minix/ipc.h
@@ -18,7 +18,7 @@ typedef struct {int m2i1, m2i2, m2i3; long m2l1, m2l2; char *m2p1;
         short m2s1;} mess_2;
 typedef struct {int m3i1, m3i2; char *m3p1; char m3ca1[M3_LONG_STRING];} mess_3;
 typedef struct {long m4l1, m4l2, m4l3, m4l4, m4l5;} mess_4;
-typedef struct {short m5c1, m5c2; int m5i1, m5i2; long m5l1, m5l2, m5l3;}mess_5;
+typedef struct {short m5s1, m5s2; int m5i1, m5i2; long m5l1, m5l2, m5l3;}mess_5;
 typedef struct {long m6l1, m6l2, m6l3; short m6s1, m6s2, m6s3; char m6c1, m6c2;
         char *m6p1, *m6p2;} mess_6;
 typedef struct {int m7i1, m7i2, m7i3, m7i4; char *m7p1, *m7p2;} mess_7;
@@ -70,8 +70,8 @@ typedef struct {
 #define m4_l4  m_u.m_m4.m4l4
 #define m4_l5  m_u.m_m4.m4l5
 
-#define m5_c1  m_u.m_m5.m5c1
-#define m5_c2  m_u.m_m5.m5c2
+#define m5_s1  m_u.m_m5.m5s1
+#define m5_s2  m_u.m_m5.m5s2
 #define m5_i1  m_u.m_m5.m5i1
 #define m5_i2  m_u.m_m5.m5i2
 #define m5_l1  m_u.m_m5.m5l1
diff --git a/kernel/system/do_copy.c b/kernel/system/do_copy.c
index 788eabcbb..544341f73 100644
--- a/kernel/system/do_copy.c
+++ b/kernel/system/do_copy.c
@@ -2,10 +2,10 @@
  *   m_type:	SYS_VIRCOPY, SYS_PHYSCOPY
  *
  * The parameters for this kernel call are:
- *    m5_c1:	CP_SRC_SPACE		source virtual segment
+ *    m5_s1:	CP_SRC_SPACE		source virtual segment
  *    m5_l1:	CP_SRC_ADDR		source offset within segment
  *    m5_i1:	CP_SRC_ENDPT		source process number
- *    m5_c2:	CP_DST_SPACE		destination virtual segment
+ *    m5_s2:	CP_DST_SPACE		destination virtual segment
  *    m5_l2:	CP_DST_ADDR		destination offset within segment
  *    m5_i2:	CP_DST_ENDPT		destination process number
  *    m5_l3:	CP_NR_BYTES		number of bytes to copy
diff --git a/kernel/system/do_irqctl.c b/kernel/system/do_irqctl.c
index 42a4d39a9..d76f1d4b6 100644
--- a/kernel/system/do_irqctl.c
+++ b/kernel/system/do_irqctl.c
@@ -2,8 +2,8 @@
  *   m_type:	SYS_IRQCTL
  *
  * The parameters for this kernel call are:
- *    m5_c1:	IRQ_REQUEST	(control operation to perform)	
- *    m5_c2:	IRQ_VECTOR	(irq line that must be controlled)
+ *    m5_s1:	IRQ_REQUEST	(control operation to perform)	
+ *    m5_s2:	IRQ_VECTOR	(irq line that must be controlled)
  *    m5_i1:	IRQ_POLICY	(irq policy allows reenabling interrupts)
  *    m5_l3:	IRQ_HOOK_ID	(provides index to be returned on interrupt)
  *      ,,          ,,          (returns index of irq hook assigned at kernel)
diff --git a/kernel/system/do_umap.c b/kernel/system/do_umap.c
index 39d59fc1f..b48453415 100644
--- a/kernel/system/do_umap.c
+++ b/kernel/system/do_umap.c
@@ -3,7 +3,7 @@
  *
  * The parameters for this kernel call are:
  *    m5_i1:	CP_SRC_PROC_NR	(process number)	
- *    m5_c1:	CP_SRC_SPACE	(segment where address is: T, D, or S)
+ *    m5_s1:	CP_SRC_SPACE	(segment where address is: T, D, or S)
  *    m5_l1:	CP_SRC_ADDR	(virtual address)	
  *    m5_l2:	CP_DST_ADDR	(returns physical address)	
  *    m5_l3:	CP_NR_BYTES	(size of datastructure)