diff --git a/src/logging.cpp b/src/logging.cpp
--- a/src/logging.cpp
+++ b/src/logging.cpp
@@ -207,6 +207,14 @@
 }
 
 bool BCLog::Logger::WillLogCategory(LogFlags category) const {
+    // ALL is not meant to be used as a logging category, but only as a mask
+    // representing all categories.
+    if (category == BCLog::NONE || category == BCLog::ALL) {
+        LogPrintf("Error trying to log using a category mask instead of an "
+                  "explicit category.");
+        return false;
+    }
+
     return (logCategories.load(std::memory_order_relaxed) & category) != 0;
 }
 
diff --git a/src/test/logging_tests.cpp b/src/test/logging_tests.cpp
new file mode 100644
--- /dev/null
+++ b/src/test/logging_tests.cpp
@@ -0,0 +1,24 @@
+// Copyright (c) 2018 The Bitcoin developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "logging.h"
+
+#include <boost/test/unit_test.hpp>
+
+BOOST_FIXTURE_TEST_SUITE(logging_tests, BasicTestingSetup)
+
+BOOST_AUTO_TEST_CASE(logging_categories) {
+    BCLog::Logger logger = GetLogger();
+
+    // Should return true for explicit categories
+    for (logFlag = 1; logFlag <= 1 << 20; logFlag++) {
+        BOOST_CHECK(logger.WillLogCategory(logFlag));
+    }
+
+    // Category masks should not log
+    BOOST_CHECK(!logger.WillLogCategory(BCLog::NONE));
+    BOOST_CHECK(!logger.WillLogCategory(BCLog::ALL));
+}
+
+BOOST_AUTO_TEST_SUITE_END()