diff -up usbguard-0.7.0/src/Library/ConfigFilePrivate.cpp.strict-config usbguard-0.7.0/src/Library/ConfigFilePrivate.cpp
--- usbguard-0.7.0/src/Library/ConfigFilePrivate.cpp.strict-config	2017-11-03 10:43:09.528657179 +0100
+++ usbguard-0.7.0/src/Library/ConfigFilePrivate.cpp	2017-11-03 11:03:51.338013408 +0100
@@ -23,6 +23,7 @@
 #include "ConfigFilePrivate.hpp"
 #include "Common/Utility.hpp"
 
+#include "usbguard/Exception.hpp"
 #include "usbguard/Logger.hpp"
 
 #include <stdexcept>
@@ -53,7 +54,7 @@ namespace usbguard
   {
     _stream.open(path, std::ios::in|std::ios::out);
     if (!_stream.is_open()) {
-      throw std::runtime_error("Can't open " + path);
+      throw Exception("Configuration", path, "unable to open the configuration file");
     }
     _dirty = false;
     parse();
@@ -62,7 +63,7 @@ namespace usbguard
   void ConfigFilePrivate::write()
   {
     if (!_stream.is_open()) {
-      throw std::runtime_error("BUG: ConfigFilePrivate::write: write() before open()");
+      throw USBGUARD_BUG("ConfigFilePrivate::write: write() before open()");
     }
 
     if (_dirty) {
@@ -116,21 +117,22 @@ namespace usbguard
     while(std::getline(_stream, config_line)) {
       ++config_line_number;
       _lines.push_back(config_line);
+      config_line = trim(config_line);
+
+      if (config_line.size() < 1 || config_line[0] == '#') {
+        continue;
+      }
 
       const size_t nv_separator = config_line.find_first_of("=");
       if (nv_separator == std::string::npos) {
-        continue;
+        throw Exception("Configuration", "line " + std::to_string(config_line_number), "syntax error");
       }
 
       std::string name = trim(config_line.substr(0, nv_separator));
-      std::string value = config_line.substr(nv_separator + 1);
-
-      if (name[0] == '#') {
-        continue;
-      }
+      std::string value = trim(config_line.substr(nv_separator + 1));
 
       if (!checkNVPair(name, value)) {
-        continue;
+        throw Exception("Configuration", name, "unknown configuration directive");
       }
 
       NVPair& setting = _settings[name];