diff --git a/compiler/systems/i_sunos.pas b/compiler/systems/i_sunos.pas
index c072173e74..363f66dcff 100644
--- a/compiler/systems/i_sunos.pas
+++ b/compiler/systems/i_sunos.pas
@@ -35,7 +35,7 @@ unit i_sunos;
             flags        : [tf_under_development,tf_files_case_sensitive,tf_use_function_relative_addresses];
             cpu          : cpu_i386;
             unit_env     : 'SOLARISUNITS';
-            extradefines : 'UNIX;LIBC';
+            extradefines : 'UNIX;LIBC;SUNOS';
             exeext       : '';
             defext       : '.def';
             scriptext    : '.sh';
@@ -93,7 +93,7 @@ unit i_sunos;
             flags        : [tf_needs_symbol_size,tf_under_development,tf_files_case_sensitive,tf_use_function_relative_addresses];
             cpu          : cpu_SPARC;
             unit_env     : 'SOLARISUNITS';
-            extradefines : 'UNIX;LIBC;';
+            extradefines : 'UNIX;LIBC;SUNOS';
             exeext       : '';
             defext       : '.def';
             scriptext    : '.sh';