diff --git a/src/libstore/daemon.cc b/src/libstore/daemon.cc
index 6079eae7b..9002a89bc 100644
--- a/src/libstore/daemon.cc
+++ b/src/libstore/daemon.cc
@@ -1025,6 +1025,7 @@ void processConnection(
 {
 #ifndef _WIN32 // TODO need graceful async exit support on Windows?
     auto monitor = !recursive ? std::make_unique<MonitorFdHup>(from.fd) : nullptr;
+    (void) monitor; // suppress warning
 #endif
 
     /* Exchange the greeting. */
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index b4a023928..c6e3af456 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -345,7 +345,7 @@ LocalStore::LocalStore(
     else if (curSchema == 0) { /* new store */
         curSchema = nixSchemaVersion;
         openDB(*state, true);
-        writeFile(schemaPath, fmt("%1%", nixSchemaVersion), 0666, true);
+        writeFile(schemaPath, fmt("%1%", curSchema), 0666, true);
     }
 
     else if (curSchema < nixSchemaVersion) {
diff --git a/src/libutil/git.cc b/src/libutil/git.cc
index af91fa643..7a9ac0bd8 100644
--- a/src/libutil/git.cc
+++ b/src/libutil/git.cc
@@ -33,7 +33,7 @@ std::optional<Mode> decodeMode(RawMode m) {
 static std::string getStringUntil(Source & source, char byte)
 {
     std::string s;
-    char n[1];
+    char n[1] = { 0 };
     source(std::string_view { n, 1 });
     while (*n != byte) {
         s += *n;
diff --git a/tests/nixos/ca-fd-leak/sender.c b/tests/nixos/ca-fd-leak/sender.c
index 75e54fc8f..44d13c990 100644
--- a/tests/nixos/ca-fd-leak/sender.c
+++ b/tests/nixos/ca-fd-leak/sender.c
@@ -19,7 +19,7 @@ int main(int argc, char **argv) {
     struct sockaddr_un data;
     data.sun_family = AF_UNIX;
     data.sun_path[0] = 0;
-    strcpy(data.sun_path + 1, argv[1]);
+    strncpy(data.sun_path + 1, argv[1], sizeof(data.sun_path) - 2);
 
     // Now try to connect, To ensure we work no matter what order we are
     // executed in, just busyloop here.
diff --git a/tests/nixos/ca-fd-leak/smuggler.c b/tests/nixos/ca-fd-leak/smuggler.c
index 82acf37e6..ae6bd5371 100644
--- a/tests/nixos/ca-fd-leak/smuggler.c
+++ b/tests/nixos/ca-fd-leak/smuggler.c
@@ -5,6 +5,7 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <assert.h>
+#include <string.h>
 
 int main(int argc, char **argv) {