diff --git a/doc/release-notes.md b/doc/release-notes.md
--- a/doc/release-notes.md
+++ b/doc/release-notes.md
@@ -5,3 +5,12 @@
 This release includes the following features and fixes:
  - Removed deprecated `getinfo` RPC.
  - Update univalue to 1.0.5
+
+Configuration
+------------
+
+* An error is issued where previously a warning was issued when a setting in
+  the config file was specified in the default section, but not overridden for
+  the selected network. This change takes only effect if the selected network
+  is not mainnet.
+
diff --git a/src/init.cpp b/src/init.cpp
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -1387,22 +1387,6 @@
                       __func__);
         }
     }
-
-    // Warn if network-specific options (-addnode, -connect, etc) are
-    // specified in default section of config file, but not overridden
-    // on the command line or in this network's section of the config file.
-    std::string network = gArgs.GetChainName();
-    for (const auto &arg : gArgs.GetUnsuitableSectionOnlyArgs()) {
-        InitWarning(strprintf(_("Config setting for %s only applied on %s "
-                                "network when in [%s] section."),
-                              arg, network, network));
-    }
-
-    // Warn if unrecognized section name are present in the config file.
-    for (const auto &section : gArgs.GetUnrecognizedSections()) {
-        InitWarning(strprintf("%s:%i " + _("Section [%s] is not recognized."),
-                              section.m_file, section.m_line, section.m_name));
-    }
 }
 
 static std::string ResolveErrMsg(const char *const optname,
@@ -1522,6 +1506,22 @@
 
     // also see: InitParameterInteraction()
 
+    // Warn if network-specific options (-addnode, -connect, etc) are
+    // specified in default section of config file, but not overridden
+    // on the command line or in this network's section of the config file.
+    std::string network = gArgs.GetChainName();
+    for (const auto &arg : gArgs.GetUnsuitableSectionOnlyArgs()) {
+        return InitError(strprintf(_("Config setting for %s only applied on %s "
+                                     "network when in [%s] section."),
+                                   arg, network, network));
+    }
+
+    // Warn if unrecognized section name are present in the config file.
+    for (const auto &section : gArgs.GetUnrecognizedSections()) {
+        InitWarning(strprintf("%s:%i " + _("Section [%s] is not recognized."),
+                              section.m_file, section.m_line, section.m_name));
+    }
+
     if (!fs::is_directory(GetBlocksDir())) {
         return InitError(
             strprintf(_("Specified blocks directory \"%s\" does not exist."),
diff --git a/test/functional/feature_config_args.py b/test/functional/feature_config_args.py
--- a/test/functional/feature_config_args.py
+++ b/test/functional/feature_config_args.py
@@ -39,6 +39,11 @@
         self.nodes[0].assert_start_raises_init_error(
             expected_msg='Error reading configuration file: parse error on line 1: -dash=1, options in configuration file must be specified without leading -')
 
+        with open(inc_conf_file_path, 'w', encoding='utf8') as conf:
+            conf.write("wallet=foo\n")
+        self.nodes[0].assert_start_raises_init_error(
+            expected_msg='Error: Config setting for -wallet only applied on regtest network when in [regtest] section.')
+
         with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
             conf.write('nono\n')
         self.nodes[0].assert_start_raises_init_error(