diff --git a/src/init.cpp b/src/init.cpp
index e64bc18f05fea..98aeca8881724 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -670,9 +670,10 @@ static void BlockNotifyCallback(bool initialSync, const CBlockIndex *pBlockIndex
         return;
 
     std::string strCmd = gArgs.GetArg("-blocknotify", "");
-
-    boost::replace_all(strCmd, "%s", pBlockIndex->GetBlockHash().GetHex());
-    boost::thread t(runCommand, strCmd); // thread runs free
+    if (!strCmd.empty()) {
+        boost::replace_all(strCmd, "%s", pBlockIndex->GetBlockHash().GetHex());
+        boost::thread t(runCommand, strCmd); // thread runs free
+    }
 }
 
 static bool fHaveGenesis = false;
diff --git a/src/util.cpp b/src/util.cpp
index 7c691d36e4ab4..48ca8a7ad91ac 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -934,6 +934,7 @@ fs::path GetSpecialFolderPath(int nFolder, bool fCreate)
 
 void runCommand(const std::string& strCommand)
 {
+    if (strCommand.empty()) return;
     int nErr = ::system(strCommand.c_str());
     if (nErr)
         LogPrintf("runCommand error: system(%s) returned %d\n", strCommand, nErr);
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index a158d4704309f..6e26a8ef3e21e 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1117,7 +1117,7 @@ bool CWallet::AddToWallet(const CWalletTx& wtxIn, bool fFlushOnClose)
     // notify an external script when a wallet transaction comes in or is updated
     std::string strCmd = gArgs.GetArg("-walletnotify", "");
 
-    if ( !strCmd.empty())
+    if (!strCmd.empty())
     {
         boost::replace_all(strCmd, "%s", wtxIn.GetHash().GetHex());
         boost::thread t(runCommand, strCmd); // thread runs free