diff --git a/application/basilisk/branding/shared/uaoverrides.inc b/application/basilisk/branding/shared/uaoverrides.inc
index e181d50b2..7d65603d2 100644
--- a/application/basilisk/branding/shared/uaoverrides.inc
+++ b/application/basilisk/branding/shared/uaoverrides.inc
@@ -9,38 +9,30 @@
 #define GK_SLICE Gecko/20100101
 #define FX_SLICE Firefox/@GK_VERSION@
 
-#ifdef XP_UNIX
-#ifndef XP_MACOSX
-#define OS_SLICE X11; Linux x86_64;
-#else
-#define OS_SLICE Macintosh; Intel Mac OS X 10.11;
-#endif
-#else
-#define OS_SLICE Windows NT 6.1; WOW64;
-#endif
+// %OS_SLICE% macro is resolved at runtime, see MoonchildProductions/UXP#1473
 
 // Mozilla overrides
-pref("@GUAO_PREF@.accounts.firefox.com", "Mozilla/5.0 (@OS_SLICE@ rv:@GK_VERSION@) @GK_SLICE@ @FX_SLICE@");
-pref("@GUAO_PREF@.addons.mozilla.org", "Mozilla/5.0 (@OS_SLICE@ rv:@GK_VERSION@) @GK_SLICE@ @FX_SLICE@");
+pref("@GUAO_PREF@.accounts.firefox.com", "Mozilla/5.0 (%OS_SLICE% rv:@GK_VERSION@) @GK_SLICE@ @FX_SLICE@");
+pref("@GUAO_PREF@.addons.mozilla.org", "Mozilla/5.0 (%OS_SLICE% rv:@GK_VERSION@) @GK_SLICE@ @FX_SLICE@");
 
 // Required for domains that have proven unresponsive to requests from users
-pref("@GUAO_PREF@.youtube.com","Mozilla/5.0 (@OS_SLICE@ rv:62.0) @GK_SLICE@ Firefox/62.0 @APP_SLICE@");
-pref("@GUAO_PREF@.gaming.youtube.com","Mozilla/5.0 (@OS_SLICE@ rv:62.0) @GK_SLICE@ Firefox/62.0");
-pref("@GUAO_PREF@.netflix.com","Mozilla/5.0 (@OS_SLICE@ rv:42.0) @GK_SLICE@ Firefox/42.0 @APP_SLICE@");
+pref("@GUAO_PREF@.youtube.com","Mozilla/5.0 (%OS_SLICE% rv:62.0) @GK_SLICE@ Firefox/62.0 @APP_SLICE@");
+pref("@GUAO_PREF@.gaming.youtube.com","Mozilla/5.0 (%OS_SLICE% rv:62.0) @GK_SLICE@ Firefox/62.0");
+pref("@GUAO_PREF@.netflix.com","Mozilla/5.0 (%OS_SLICE% rv:42.0) @GK_SLICE@ Firefox/42.0 @APP_SLICE@");
 
 // The never-ending Facebook debacle...
 
 // UA-Sniffing domains below are pending responses from their operators - temp workaround
 // Daily motion only likes strict Firefox UAs
-pref("@GUAO_PREF@.dailymotion.com","Mozilla/5.0 (@OS_SLICE@ rv:52.0) @GK_SLICE@ Firefox/52.0");
+pref("@GUAO_PREF@.dailymotion.com","Mozilla/5.0 (%OS_SLICE% rv:52.0) @GK_SLICE@ Firefox/52.0");
 
 // The following requires native mode. Or it blocks.. "too old firefox", breakage, etc.
 
 // UA-Sniffing domains below have indicated no interest in supporting Pale Moon (BOO!)
-pref("@GUAO_PREF@.whatsapp.com","Mozilla/5.0 (@OS_SLICE@ rv:61.0) @GK_SLICE@ Firefox/61.0");
+pref("@GUAO_PREF@.whatsapp.com","Mozilla/5.0 (%OS_SLICE% rv:61.0) @GK_SLICE@ Firefox/61.0");
 
 // UA-sniffing domains that are "app/vendor-specific" and do not like Pale Moon
 
 // The following domains do not like the Goanna slice
-pref("@GUAO_PREF@.hitbox.tv","Mozilla/5.0 (@OS_SLICE@ rv:@GK_VERSION@) @GK_SLICE@ @FX_SLICE@");
-pref("@GUAO_PREF@.yuku.com","Mozilla/5.0 (@OS_SLICE@ rv:@GK_VERSION@) @GK_SLICE@ @FX_SLICE@ @APP_SLICE@");
+pref("@GUAO_PREF@.hitbox.tv","Mozilla/5.0 (%OS_SLICE% rv:@GK_VERSION@) @GK_SLICE@ @FX_SLICE@");
+pref("@GUAO_PREF@.yuku.com","Mozilla/5.0 (%OS_SLICE% rv:@GK_VERSION@) @GK_SLICE@ @FX_SLICE@ @APP_SLICE@");