diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index b16a9945f6..292ff224e7 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -2850,6 +2850,9 @@ void PeerManagerImpl::ProcessMessage(
 
         vRecv >> nVersion >> nServiceInt >> nTime >> addrMe;
         nSendVersion = std::min(nVersion, PROTOCOL_VERSION);
+        if (nTime < 0) {
+            nTime = 0;
+        }
         nServices = ServiceFlags(nServiceInt);
         if (!pfrom.fInbound)
         {
diff --git a/src/rpc/misc.cpp b/src/rpc/misc.cpp
index c4cf607f61..fcab8d4b1b 100644
--- a/src/rpc/misc.cpp
+++ b/src/rpc/misc.cpp
@@ -522,7 +522,7 @@ static UniValue setmocktime(const JSONRPCRequest& request)
         "\nSet the local time to given timestamp (-regtest only)\n",
         {
             {"timestamp", RPCArg::Type::NUM, RPCArg::Optional::NO, UNIX_EPOCH_TIME + "\n"
-    "   Pass 0 to go back to using the system time."},
+             "Pass 0 to go back to using the system time."},
         },
         RPCResult{RPCResult::Type::NONE, "", ""},
         RPCExamples{""},
@@ -540,7 +540,10 @@ static UniValue setmocktime(const JSONRPCRequest& request)
     LOCK(cs_main);
 
     RPCTypeCheck(request.params, {UniValue::VNUM});
-    int64_t time = request.params[0].get_int64();
+    const int64_t time{request.params[0].get_int64()};
+    if (time < 0) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Mocktime can not be negative: %s.", time));
+    }
     SetMockTime(time);
     if (auto* node_context = GetContext<NodeContext>(request.context)) {
         for (const auto& chain_client : node_context->chain_clients) {
diff --git a/src/util/time.cpp b/src/util/time.cpp
index 900f8777f2..718e13fded 100644
--- a/src/util/time.cpp
+++ b/src/util/time.cpp
@@ -10,6 +10,8 @@
 #include <compat.h>
 #include <util/time.h>
 
+#include <util/check.h>
+
 #include <atomic>
 #include <boost/date_time/posix_time/posix_time.hpp>
 #include <ctime>
@@ -19,7 +21,7 @@
 
 void UninterruptibleSleep(const std::chrono::microseconds& n) { std::this_thread::sleep_for(n); }
 
-static std::atomic<int64_t> nMockTime(0); //!< For unit testing
+static std::atomic<int64_t> nMockTime(0); //!< For testing
 
 int64_t GetTime()
 {
@@ -47,6 +49,7 @@ template std::chrono::microseconds GetTime();
 
 void SetMockTime(int64_t nMockTimeIn)
 {
+    Assert(nMockTimeIn >= 0);
     nMockTime.store(nMockTimeIn, std::memory_order_relaxed);
 }
 
diff --git a/test/functional/rpc_uptime.py b/test/functional/rpc_uptime.py
index f7c9e4611d..645d76cdfa 100755
--- a/test/functional/rpc_uptime.py
+++ b/test/functional/rpc_uptime.py
@@ -10,6 +10,7 @@ Test corresponds to code in rpc/server.cpp.
 import time
 
 from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_raises_rpc_error
 
 
 class UptimeTest(BitcoinTestFramework):
@@ -18,8 +19,12 @@ class UptimeTest(BitcoinTestFramework):
         self.setup_clean_chain = True
 
     def run_test(self):
+        self._test_negative_time()
         self._test_uptime()
 
+    def _test_negative_time(self):
+        assert_raises_rpc_error(-8, "Mocktime can not be negative: -1.", self.nodes[0].setmocktime, -1)
+
     def _test_uptime(self):
         wait_time = 10
         self.nodes[0].setmocktime(int(time.time() + wait_time))