diff --git a/libtcc.c b/libtcc.c
index 58a5ca07..e5383211 100644
--- a/libtcc.c
+++ b/libtcc.c
@@ -1080,6 +1080,12 @@ ST_FUNC int tcc_add_file_internal(TCCState *s1, const char *filename, int flags)
     if (ext[0])
         ext++;
 
+#ifdef CONFIG_TCC_ASM
+    /* if .S file, define __ASSEMBLER__ like gcc does */
+    if (!strcmp(ext, "S"))
+        tcc_define_symbol(s1, "__ASSEMBLER__", NULL);
+#endif
+
     /* open the file */
     ret = tcc_open(s1, filename);
     if (ret < 0) {
diff --git a/tests/asmtest.S b/tests/asmtest.S
index f6fecde5..0d4c0fc9 100644
--- a/tests/asmtest.S
+++ b/tests/asmtest.S
@@ -564,3 +564,7 @@ int $0x10
     pushl $1
     pushw $1
     push $1
+
+#ifdef __ASSEMBLER__ // should be defined, for S files
+    inc %eax
+#endif