diff --git a/lib/libpmc/libpmc_pmu_util.c b/lib/libpmc/libpmc_pmu_util.c
--- a/lib/libpmc/libpmc_pmu_util.c
+++ b/lib/libpmc/libpmc_pmu_util.c
@@ -577,6 +577,7 @@
 pmc_pmu_pmcallocate(const char *event_name, struct pmc_op_pmcallocate *pm)
 {
 	const struct pmu_event *pe;
+	struct pmu_event_desc ped;
 	int idx = -1;
 
 	event_name = pmu_alias_get(event_name);
@@ -584,8 +585,12 @@
 		return (ENOENT);
 	if (pe->event == NULL)
 		return (ENOENT);
+	if (pmu_parse_event(&ped, pe->event))
+		return (ENOENT);
 
 	assert(idx >= 0);
+	pm->pm_ev = idx;
+	pm->pm_md.pm_md_config = ped.ped_event;
 	pm->pm_md.pm_md_flags |= PM_MD_RAW_EVENT;
 	pm->pm_class = PMC_CLASS_ARMV8;
 	pm->pm_caps |= (PMC_CAP_READ | PMC_CAP_WRITE);
diff --git a/sys/arm64/include/pmc_mdep.h b/sys/arm64/include/pmc_mdep.h
--- a/sys/arm64/include/pmc_mdep.h
+++ b/sys/arm64/include/pmc_mdep.h
@@ -38,10 +38,12 @@
 #include <dev/hwpmc/hwpmc_arm64.h>
 
 union pmc_md_op_pmcallocate {
-	uint32_t		pm_md_flags;
+	struct {
+		uint32_t	pm_md_config;
+		uint32_t	pm_md_flags;
 #define	PM_MD_RAW_EVENT		0x1
-	uint32_t		__pad32;
-	uint64_t		__pad[3];
+	};
+	uint64_t		__pad[4];
 };
 
 /* Logging */
diff --git a/sys/dev/hwpmc/hwpmc_arm64.c b/sys/dev/hwpmc/hwpmc_arm64.c
--- a/sys/dev/hwpmc/hwpmc_arm64.c
+++ b/sys/dev/hwpmc/hwpmc_arm64.c
@@ -182,9 +182,9 @@
 	pe = a->pm_ev;
 
 	/* Adjust the config value if needed. */
-	config = (uint32_t)pe;
+	config = a->pm_md.pm_md_config;
 	if ((a->pm_md.pm_md_flags & PM_MD_RAW_EVENT) == 0) {
-		config -= PMC_EV_ARMV8_FIRST;
+		config = (uint32_t)pe - PMC_EV_ARMV8_FIRST;
 		if (config > (PMC_EV_ARMV8_LAST - PMC_EV_ARMV8_FIRST))
 			return (EINVAL);
 	}