diff --git a/netd/BpfHandler.cpp b/netd/BpfHandler.cpp
index 925ee50..aa84089 100644
--- a/netd/BpfHandler.cpp
+++ b/netd/BpfHandler.cpp
@@ -181,7 +181,27 @@
     return netdutils::status::ok;
 }
 
+static void mapLockTest(void) {
+    // The maps must be R/W, and as yet unopened (or more specifically not yet lock'ed).
+    const char * const m1 = BPF_NETD_PATH "map_netd_lock_array_test_map";
+    const char * const m2 = BPF_NETD_PATH "map_netd_lock_hash_test_map";
+
+    unique_fd fd0(bpf::mapRetrieveExclusiveRW(m1)); if (!fd0.ok()) abort();
+
+    unique_fd fd1(bpf::mapRetrieveExclusiveRW(m2)); if (!fd1.ok()) abort();  // no conflict with fd0
+    unique_fd fd2(bpf::mapRetrieveExclusiveRW(m2)); if ( fd2.ok()) abort();  // busy due to fd1
+    unique_fd fd3(bpf::mapRetrieveRO(m2));          if (!fd3.ok()) abort();  // no lock taken
+    unique_fd fd4(bpf::mapRetrieveRW(m2));          if ( fd4.ok()) abort();  // busy due to fd1
+    fd1.reset();  // releases exclusive lock
+    unique_fd fd5(bpf::mapRetrieveRO(m2));          if (!fd5.ok()) abort();  // no lock taken
+    unique_fd fd6(bpf::mapRetrieveRW(m2));          if (!fd6.ok()) abort();  // now ok
+    unique_fd fd7(bpf::mapRetrieveRO(m2));          if (!fd7.ok()) abort();  // no lock taken
+    unique_fd fd8(bpf::mapRetrieveExclusiveRW(m2)); if ( fd8.ok()) abort();  // busy due to fd6
+}
+
 Status BpfHandler::initMaps() {
+    mapLockTest();
+
     RETURN_IF_NOT_OK(mStatsMapA.init(STATS_MAP_A_PATH));
     RETURN_IF_NOT_OK(mStatsMapB.init(STATS_MAP_B_PATH));
     RETURN_IF_NOT_OK(mConfigurationMap.init(CONFIGURATION_MAP_PATH));