diff --git a/headless/Headless.cpp b/headless/Headless.cpp
index 1f58b1f87e..006a37700f 100644
--- a/headless/Headless.cpp
+++ b/headless/Headless.cpp
@@ -752,6 +752,12 @@ int main(int argc, const char* argv[]) {
 
 	std::string error_string;
 
+	// Headless never loads a config file, so without this every setting not named below keeps the
+	// zero-initialized value instead of its real default, and headless runs games differently from
+	// every other build (bFastMemory and bFuncReplacements are both "true" defaults that came out
+	// false that way). Apply the defaults first, then force the values the tests want.
+	g_Config.RestoreDefaults(RestoreSettingsBits::SETTINGS, false);
+
 	// Force known values for deterministic test execution. This happens before
 	// ApplyToConfig() below, so a matching command line flag can still override any of it -
 	// ApplyToConfig() always has the final say on the settings in g_Config.