diff --git a/src/comm/comm_client.cpp b/src/comm/comm_client.cpp
index d428671c..025946ce 100644
--- a/src/comm/comm_client.cpp
+++ b/src/comm/comm_client.cpp
@@ -52,6 +52,8 @@ namespace comm
             {
                 close(read_fd);
                 close(write_fd);
+                
+                util::kill_process(pid, false);
                 return -1;
             }
 
diff --git a/src/comm/comm_server.cpp b/src/comm/comm_server.cpp
index 7b8a1717..52c5be21 100644
--- a/src/comm/comm_server.cpp
+++ b/src/comm/comm_server.cpp
@@ -312,8 +312,9 @@ namespace comm
                 close(firewall_pipe[0]);
 
             // Wait for some time and check if websocketd is still running properly.
+            // Sending signal 0 to test whether process exist.
             util::sleep(20);
-            if (kill(pid, 0) == -1)
+            if (util::kill_process(pid, false, 0) == -1)
                 return -1;
 
             websocketd_pid = pid;
diff --git a/src/hpfs/hpfs.cpp b/src/hpfs/hpfs.cpp
index b5b839f4..c78d8cad 100644
--- a/src/hpfs/hpfs.cpp
+++ b/src/hpfs/hpfs.cpp
@@ -40,9 +40,11 @@ namespace hpfs
         if (pid > 0)
         {
             // HotPocket process.
-            // Check if process is still running.
-            util::sleep(20);
-            if (kill(pid, 0) == -1)
+            util::sleep(INIT_CHECK_INTERVAL);
+
+            // Check if hpfs process is still running.
+            // Sending signal 0 to test whether process exist.
+            if (util::kill_process(pid, false, 0) == -1)
                 return -1;
 
             merge_pid = pid;
@@ -102,8 +104,9 @@ namespace hpfs
             {
                 util::sleep(INIT_CHECK_INTERVAL);
 
-                // Check if process is still running.
-                if (kill(pid, 0) == -1)
+                // Check if hpfs process is still running.
+                // Sending signal 0 to test whether process exist.
+                if (util::kill_process(pid, false, 0) == -1)
                 {
                     LOG_ERR << "hpfs process " << pid << " has stopped.";
                     break;
diff --git a/src/sc.cpp b/src/sc.cpp
index 1963033b..66b9a819 100644
--- a/src/sc.cpp
+++ b/src/sc.cpp
@@ -40,7 +40,11 @@ namespace sc
 
             // Write the inputs into the contract process.
             if (feed_inputs(ctx) != 0)
+            {
+                util::kill_process(pid, true);
+                ctx.contract_pid = 0;
                 goto failure;
+            }
 
             // Wait for child process (contract process) to complete execution.
             const int presult = await_process_execution(ctx.contract_pid);
diff --git a/src/util.cpp b/src/util.cpp
index 48f92d05..5638713d 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -215,7 +215,7 @@ namespace util
         pthread_sigmask(SIG_SETMASK, &mask, NULL);
     }
 
-    // Kill a process with a signal and wait until it stops running.
+    // Kill a process with a signal and if specified, wait until it stops running.
     int kill_process(const pid_t pid, const bool wait, const int signal)
     {
         if (kill(pid, signal) == -1)
@@ -224,8 +224,8 @@ namespace util
             return -1;
         }
 
-        int pid_status;
-        if (wait && waitpid(pid, &pid_status, 0) == -1)
+        const int wait_options = wait ? 0 : WNOHANG;
+        if (waitpid(pid, NULL, wait_options) == -1)
         {
             LOG_ERR << errno << ": waitpid after kill failed.";
             return -1;