diff --git a/assemble_aux.c b/assemble_aux.c
index 894342c..0eaac76 100644
--- a/assemble_aux.c
+++ b/assemble_aux.c
@@ -469,17 +469,17 @@ void mode_extension(
 
     if (value->type == EX_LIT) {
         if (mode->rel) {              /* PC-relative? */
-	    if (current_pc->section->flags & PSECT_REL) {
-		store_displaced_word(str, tr, 2, value->data.lit);
-	    } else {
+            if (current_pc->section->flags & PSECT_REL) {
+                store_displaced_word(str, tr, 2, value->data.lit);
+            } else {
                 /* I can compute this myself. */
-		store_word(str, tr, 2, value->data.lit - DOT - 2);
-	    }
-	} else {
+                store_word(str, tr, 2, value->data.lit - DOT - 2);
+            }
+        } else {
             store_word(str, tr, 2, value->data.lit);    /* Just a
                                                            known
                                                            value. */
-	}
+        }
     } else if (express_sym_offset(value, &sym, &offset)) {
         if ((sym->flags & (SYMBOLFLAG_GLOBAL | SYMBOLFLAG_DEFINITION)) == SYMBOLFLAG_GLOBAL) {
             /* Reference to a global symbol. */
diff --git a/assemble_globals.c b/assemble_globals.c
index 3311c2d..014693b 100644
--- a/assemble_globals.c
+++ b/assemble_globals.c
@@ -24,7 +24,7 @@ int             last_locsym = 32768;    /* The last local symbol number generate
 
 int             enabl_debug = 0;        /* Whether assembler debugging is enabled */
 
-int             opt_enabl_ama = 0; 	/* May be changed by command line */
+int             opt_enabl_ama = 0;      /* May be changed by command line */
 int             enabl_ama;      /* When set, chooses absolute (037) versus
                                    PC-relative */
                                 /* (067) addressing mode */
diff --git a/assemble_globals.h b/assemble_globals.h
index df43e4b..4a21eb2 100644
--- a/assemble_globals.h
+++ b/assemble_globals.h
@@ -35,7 +35,7 @@ extern int      last_locsym;    /* The last local symbol number generated */
 
 extern int      enabl_debug;    /* Whether assembler debugging is enabled */
 
-extern int      opt_enabl_ama; 	/* May be changed by command line */
+extern int      opt_enabl_ama;  /* May be changed by command line */
 
 extern int      enabl_ama;      /* When set, chooses absolute (037) versus
                                    PC-relative */
diff --git a/extree.h b/extree.h
index 645af17..67ae797 100644
--- a/extree.h
+++ b/extree.h
@@ -32,9 +32,9 @@ typedef struct ex_tree {
         EX_AND = 12,
         /* bitwise and */
         EX_OR = 13,
-	/* bitwise or */
+        /* bitwise or */
         EX_LSH = 14
-	/* left shift */
+        /* left shift */
     } type;
 
     char           *cp;         /* points to end of parsed expression */
diff --git a/macro11.c b/macro11.c
index 112946b..49c84a3 100644
--- a/macro11.c
+++ b/macro11.c
@@ -63,7 +63,7 @@ static void enable_tf(
     if (strcmp(opt, "AMA") == 0)
         opt_enabl_ama = tf;
     else if (strcmp(opt, "GBL") == 0)
-        enabl_gbl = tf;		/* Unused in pass 2 */
+        enabl_gbl = tf;         /* Unused in pass 2 */
     else if (strcmp(opt, "ME") == 0)
         list_me = tf;
     else if (strcmp(opt, "BEX") == 0)
diff --git a/parse.h b/parse.h
index 9739c98..c67f064 100644
--- a/parse.h
+++ b/parse.h
@@ -8,8 +8,8 @@
 
 // is char 'c' part of a symbol?
 #define issym(c) (isalpha(c) || isdigit(c) \
-		|| (c) == '.' || (c) == '$' \
-		|| (symbol_allow_underscores && (c) == '_'))
+                || (c) == '.' || (c) == '$' \
+                || (symbol_allow_underscores && (c) == '_'))
 
 
 char           *skipwhite(