diff --git a/src/banman.cpp b/src/banman.cpp
--- a/src/banman.cpp
+++ b/src/banman.cpp
@@ -114,11 +114,15 @@
                  int64_t bantimeoffset, bool sinceUnixEpoch) {
     CBanEntry banEntry(GetTime());
     banEntry.banReason = banReason;
+
+    int64_t normalized_bantimeoffset = bantimeoffset;
+    bool normalized_sinceUnixEpoch = sinceUnixEpoch;
     if (bantimeoffset <= 0) {
-        bantimeoffset = m_default_ban_time;
-        sinceUnixEpoch = false;
+        normalized_bantimeoffset = m_default_ban_time;
+        normalized_sinceUnixEpoch = false;
     }
-    banEntry.nBanUntil = (sinceUnixEpoch ? 0 : GetTime()) + bantimeoffset;
+    banEntry.nBanUntil =
+        (normalized_sinceUnixEpoch ? 0 : GetTime()) + normalized_bantimeoffset;
 
     {
         LOCK(m_cs_banned);