diff --git a/libtcc.c b/libtcc.c
index fbc2e50..e25381e 100644
--- a/libtcc.c
+++ b/libtcc.c
@@ -1146,10 +1146,13 @@ ST_FUNC int tcc_add_file_internal(TCCState *s1, const char *filename, int flags)
     if (ext[0])
         ext++;
 
+    parse_flags = 0;
 #ifdef CONFIG_TCC_ASM
     /* if .S file, define __ASSEMBLER__ like gcc does */
-    if (!strcmp(ext, "S"))
+    if (!strcmp(ext, "S") || !strcmp(ext, "s")) {
         tcc_define_symbol(s1, "__ASSEMBLER__", NULL);
+        parse_flags = PARSE_FLAG_ASM_FILE;
+    }
 #endif
 
     /* open the file */
diff --git a/tcc.h b/tcc.h
index e25a55b..3e8d9aa 100644
--- a/tcc.h
+++ b/tcc.h
@@ -1149,6 +1149,7 @@ ST_DATA TokenSym **table_ident;
                                         returned at eof */
 #define PARSE_FLAG_ASM_COMMENTS 0x0008 /* '#' can be used for line comment */
 #define PARSE_FLAG_SPACES     0x0010 /* next() returns space tokens (for -E) */
+#define PARSE_FLAG_ASM_FILE 0x0020 /* we processing an asm file */
 
 ST_FUNC TokenSym *tok_alloc(const char *str, int len);
 ST_FUNC char *get_tok_str(int v, CValue *cv);
diff --git a/tccpp.c b/tccpp.c
index 1d41d6b..f38e41a 100644
--- a/tccpp.c
+++ b/tccpp.c
@@ -782,6 +782,8 @@ redo_start:
                 else if (parse_flags & PARSE_FLAG_ASM_COMMENTS)
             	    p = parse_line_comment(p);
             }
+            else if (parse_flags & PARSE_FLAG_ASM_FILE)
+        	p = parse_line_comment(p);
             break;
 _default:
         default:
@@ -1432,7 +1434,7 @@ ST_FUNC void preprocess(int is_bof)
     saved_parse_flags = parse_flags;
     parse_flags = PARSE_FLAG_PREPROCESS | PARSE_FLAG_TOK_NUM | 
         PARSE_FLAG_LINEFEED;
-    parse_flags |= (saved_parse_flags & PARSE_FLAG_ASM_COMMENTS);
+    parse_flags |= (saved_parse_flags & (PARSE_FLAG_ASM_FILE | PARSE_FLAG_ASM_COMMENTS));
     next_nomacro();
  redo:
     switch(tok) {
@@ -2259,6 +2261,11 @@ maybe_newline:
     case '#':
         /* XXX: simplify */
         PEEKC(c, p);
+        if (is_space(c) && (parse_flags & PARSE_FLAG_ASM_FILE)) {
+    	    p = parse_line_comment(p);
+            goto redo_no_start;
+        }
+        else
         if ((tok_flags & TOK_FLAG_BOL) && 
             (parse_flags & PARSE_FLAG_PREPROCESS)) {
             file->buf_ptr = p;
@@ -2588,7 +2595,12 @@ maybe_newline:
         p++;
         break;
     default:
-        tcc_error("unrecognized character \\x%02x", c);
+	if ((parse_flags & PARSE_FLAG_ASM_FILE) == 0)
+    	    tcc_error("unrecognized character \\x%02x", c);
+    	else {
+    	    tok = ' ';
+    	    p++;
+    	}
         break;
     }
     tok_flags = 0;
@@ -3215,7 +3227,8 @@ ST_FUNC int tcc_preprocess(TCCState *s1)
     preprocess_init(s1);
     ch = file->buf_ptr[0];
     tok_flags = TOK_FLAG_BOL | TOK_FLAG_BOF;
-    parse_flags = PARSE_FLAG_ASM_COMMENTS | PARSE_FLAG_PREPROCESS |
+    parse_flags = (parse_flags & PARSE_FLAG_ASM_FILE);
+    parse_flags |= PARSE_FLAG_ASM_COMMENTS | PARSE_FLAG_PREPROCESS |
         PARSE_FLAG_LINEFEED | PARSE_FLAG_SPACES;
     token_seen = 0;
     file->line_ref = 0;