diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index a27024e45a..6760823e13 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -1555,7 +1555,7 @@ static void spapr_pci_pre_plug(HotplugHandler *plug_handler,
          */
         if (plugged_dev->hotplugged) {
             error_setg(errp, QERR_BUS_NO_HOTPLUG,
-                       object_get_typename(OBJECT(phb)));
+                       phb->parent_obj.bus->qbus.name);
             return;
         }
     }
@@ -1676,7 +1676,7 @@ static void spapr_pci_unplug_request(HotplugHandler *plug_handler,
 
     if (!phb->dr_enabled) {
         error_setg(errp, QERR_BUS_NO_HOTPLUG,
-                   object_get_typename(OBJECT(phb)));
+                   phb->parent_obj.bus->qbus.name);
         return;
     }
 
diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
index 6c559b48c8..871898ac46 100644
--- a/monitor/hmp-cmds.c
+++ b/monitor/hmp-cmds.c
@@ -24,7 +24,6 @@
 #include "qapi/qapi-commands-control.h"
 #include "qapi/qapi-commands-misc.h"
 #include "qapi/qmp/qdict.h"
-#include "qapi/qmp/qerror.h"
 #include "qemu/cutils.h"
 #include "hw/intc/intc.h"
 #include "qemu/log.h"
@@ -138,7 +137,8 @@ void hmp_sync_profile(Monitor *mon, const QDict *qdict)
     } else {
         Error *err = NULL;
 
-        error_setg(&err, QERR_INVALID_PARAMETER, op);
+        error_setg(&err, "invalid parameter '%s',"
+                   " expecting 'on', 'off', or 'reset'", op);
         hmp_handle_error(mon, err);
     }
 }
diff --git a/net/net.c b/net/net.c
index c0c0cbe99e..8e67a20abc 100644
--- a/net/net.c
+++ b/net/net.c
@@ -1227,7 +1227,7 @@ static int net_client_init(QemuOpts *opts, bool is_netdev, Error **errp)
     int ret = -1;
     Visitor *v = opts_visitor_new(opts);
 
-    /* Parse convenience option format ip6-net=fec0::0[/64] */
+    /* Parse convenience option format ipv6-net=fec0::0[/64] */
     const char *ip6_net = qemu_opt_get(opts, "ipv6-net");
 
     if (ip6_net) {
@@ -1247,8 +1247,8 @@ static int net_client_init(QemuOpts *opts, bool is_netdev, Error **errp)
         if (substrings[1] &&
             qemu_strtoul(substrings[1], NULL, 10, &prefix_len))
         {
-            error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
-                       "ipv6-prefixlen", "a number");
+            error_setg(errp,
+                       "parameter 'ipv6-net' expects a number after '/'");
             goto out;
         }
 
diff --git a/qga/commands.c b/qga/commands.c
index ce172edd2d..88c1c99fe5 100644
--- a/qga/commands.c
+++ b/qga/commands.c
@@ -154,7 +154,7 @@ GuestExecStatus *qmp_guest_exec_status(int64_t pid, Error **errp)
 
     gei = guest_exec_info_find(pid);
     if (gei == NULL) {
-        error_setg(errp, QERR_INVALID_PARAMETER, "pid");
+        error_setg(errp, "PID " PRId64 " does not exist");
         return NULL;
     }
 
diff --git a/system/balloon.c b/system/balloon.c
index e0e8969a4b..fda7af832e 100644
--- a/system/balloon.c
+++ b/system/balloon.c
@@ -90,17 +90,17 @@ BalloonInfo *qmp_query_balloon(Error **errp)
     return info;
 }
 
-void qmp_balloon(int64_t target, Error **errp)
+void qmp_balloon(int64_t value, Error **errp)
 {
     if (!have_balloon(errp)) {
         return;
     }
 
-    if (target <= 0) {
-        error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "target", "a size");
+    if (value <= 0) {
+        error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "value", "a size");
         return;
     }
 
-    trace_balloon_event(balloon_opaque, target);
-    balloon_event_fn(balloon_opaque, target);
+    trace_balloon_event(balloon_opaque, value);
+    balloon_event_fn(balloon_opaque, value);
 }
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 358d9c0a65..cd16cb893d 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -5192,7 +5192,8 @@ static void x86_cpuid_set_vendor(Object *obj, const char *value,
     int i;
 
     if (strlen(value) != CPUID_VENDOR_SZ) {
-        error_setg(errp, QERR_PROPERTY_VALUE_BAD, "", "vendor", value);
+        error_setg(errp, "value of property 'vendor' must consist of"
+                   " exactly " stringify(CPUID_VENDOR_SZ) " characters");
         return;
     }
 
diff --git a/ui/ui-qmp-cmds.c b/ui/ui-qmp-cmds.c
index d772e1cb7f..74fa6c6ec5 100644
--- a/ui/ui-qmp-cmds.c
+++ b/ui/ui-qmp-cmds.c
@@ -44,7 +44,8 @@ void qmp_set_password(SetPasswordOptions *opts, Error **errp)
         assert(opts->protocol == DISPLAY_PROTOCOL_VNC);
         if (opts->connected != SET_PASSWORD_ACTION_KEEP) {
             /* vnc supports "connected=keep" only */
-            error_setg(errp, QERR_INVALID_PARAMETER, "connected");
+            error_setg(errp, "parameter 'connected' must be 'keep'"
+                       " when 'protocol' is 'vnc'");
             return;
         }
         /*
@@ -195,7 +196,7 @@ void qmp_client_migrate_info(const char *protocol, const char *hostname,
         }
 
         if (!has_port && !has_tls_port) {
-            error_setg(errp, QERR_MISSING_PARAMETER, "port/tls-port");
+            error_setg(errp, "parameter 'port' or 'tls-port' is required");
             return;
         }