diff --git a/src/os/darwin/darwin_sigar.c b/src/os/darwin/darwin_sigar.c
index 6c1334fa..2aa5d7fe 100644
--- a/src/os/darwin/darwin_sigar.c
+++ b/src/os/darwin/darwin_sigar.c
@@ -940,6 +940,7 @@ int sigar_proc_state_get(sigar_t *sigar, sigar_pid_t pid,
     procstate->priority = pinfo->KI_PRI;
     procstate->nice     = pinfo->KI_NICE;
     procstate->tty      = SIGAR_FIELD_NOTIMPL; /*XXX*/
+    procstate->threads  = SIGAR_FIELD_NOTIMPL;
 
     switch (pinfo->KI_STAT) {
       case SIDL:
diff --git a/src/os/netware/netware_sigar.c b/src/os/netware/netware_sigar.c
index 25304804..769d9ca3 100644
--- a/src/os/netware/netware_sigar.c
+++ b/src/os/netware/netware_sigar.c
@@ -214,6 +214,7 @@ int sigar_proc_state_get(sigar_t *sigar, sigar_pid_t pid,
     procstate->nice = -1;
     procstate->tty = -1;
     procstate->state = 'R';
+    procstate->threads = -1;
 
     return SIGAR_OK;
 }
diff --git a/src/os/osf1/osf1_sigar.c b/src/os/osf1/osf1_sigar.c
index f9f23177..435835af 100644
--- a/src/os/osf1/osf1_sigar.c
+++ b/src/os/osf1/osf1_sigar.c
@@ -279,6 +279,7 @@ int sigar_proc_state_get(sigar_t *sigar, sigar_pid_t pid,
     procstate->priority = SIGAR_FIELD_NOTIMPL;
     procstate->nice = SIGAR_FIELD_NOTIMPL;
     procstate->tty = info.pi_ttyd;
+    procstate->threads = SIGAR_FIELD_NOTIMPL;
 
     switch (info.pi_status) {
       case PI_ACTIVE:
diff --git a/src/os/stub/stub_sigar.c b/src/os/stub/stub_sigar.c
index 3c9ac6ef..fe1ef24f 100644
--- a/src/os/stub/stub_sigar.c
+++ b/src/os/stub/stub_sigar.c
@@ -136,6 +136,7 @@ int sigar_proc_state_get(sigar_t *sigar, sigar_pid_t pid,
     procstate->nice = -1;
     procstate->tty = -1;
     procstate->state = 'R';
+    procstate->threads = -1;
 
     return SIGAR_OK;
 }