diff --git a/sys/powerpc/powerpc/intr_machdep.c b/sys/powerpc/powerpc/intr_machdep.c
--- a/sys/powerpc/powerpc/intr_machdep.c
+++ b/sys/powerpc/powerpc/intr_machdep.c
@@ -129,6 +129,7 @@
 #endif
 static u_int stray_count;
 
+#define	INTRNAME_LEN	(MAXCOMLEN + 1)
 u_long *intrcnt;
 char *intrnames;
 size_t sintrcnt = sizeof(intrcnt);
@@ -154,8 +155,8 @@
 intrcnt_setname(const char *name, int index)
 {
 
-	snprintf(intrnames + (MAXCOMLEN + 1) * index, MAXCOMLEN + 1, "%-*s",
-	    MAXCOMLEN, name);
+	snprintf(intrnames + INTRNAME_LEN * index, INTRNAME_LEN, "%-*s",
+	    INTRNAME_LEN - 1, name);
 }
 
 static void
@@ -179,10 +180,10 @@
 #endif
 	intrcnt = mallocarray(nintrcnt, sizeof(u_long), M_INTR, M_WAITOK |
 	    M_ZERO);
-	intrnames = mallocarray(nintrcnt, MAXCOMLEN + 1, M_INTR, M_WAITOK |
+	intrnames = mallocarray(nintrcnt, INTRNAME_LEN, M_INTR, M_WAITOK |
 	    M_ZERO);
 	sintrcnt = nintrcnt * sizeof(u_long);
-	sintrnames = nintrcnt * (MAXCOMLEN + 1);
+	sintrnames = nintrcnt * INTRNAME_LEN;
 
 	intrcnt_setname("???", 0);
 	intrcnt_index = 1;
diff --git a/sys/x86/x86/intr_machdep.c b/sys/x86/x86/intr_machdep.c
--- a/sys/x86/x86/intr_machdep.c
+++ b/sys/x86/x86/intr_machdep.c
@@ -95,6 +95,7 @@
 static int assign_cpu;
 #endif
 
+#define	INTRNAME_LEN	(MAXCOMLEN + 1)
 u_long *intrcnt;
 char *intrnames;
 size_t sintrcnt = sizeof(intrcnt);
@@ -189,10 +190,10 @@
 #endif
 	intrcnt = mallocarray(nintrcnt, sizeof(u_long), M_INTR, M_WAITOK |
 	    M_ZERO);
-	intrnames = mallocarray(nintrcnt, MAXCOMLEN + 1, M_INTR, M_WAITOK |
+	intrnames = mallocarray(nintrcnt, INTRNAME_LEN, M_INTR, M_WAITOK |
 	    M_ZERO);
 	sintrcnt = nintrcnt * sizeof(u_long);
-	sintrnames = nintrcnt * (MAXCOMLEN + 1);
+	sintrnames = nintrcnt * INTRNAME_LEN;
 
 	intrcnt_setname("???", 0);
 	intrcnt_index = 1;
@@ -430,8 +431,8 @@
 intrcnt_setname(const char *name, int index)
 {
 
-	snprintf(intrnames + (MAXCOMLEN + 1) * index, MAXCOMLEN + 1, "%-*s",
-	    MAXCOMLEN, name);
+	snprintf(intrnames + INTRNAME_LEN * index, INTRNAME_LEN, "%-*s",
+	    INTRNAME_LEN - 1, name);
 }
 
 static void
@@ -444,14 +445,14 @@
 static void
 intrcnt_register(struct intsrc *is)
 {
-	char straystr[MAXCOMLEN + 1];
+	char straystr[INTRNAME_LEN];
 
 	KASSERT(is->is_event != NULL, ("%s: isrc with no event", __func__));
 	mtx_lock_spin(&intrcnt_lock);
 	MPASS(intrcnt_index + 2 <= nintrcnt);
 	is->is_index = intrcnt_index;
 	intrcnt_index += 2;
-	snprintf(straystr, MAXCOMLEN + 1, "stray irq%d",
+	snprintf(straystr, sizeof(straystr), "stray irq%d",
 	    is->is_pic->pic_vector(is));
 	intrcnt_updatename(is);
 	is->is_count = &intrcnt[is->is_index];