diff --git a/macros.c b/macros.c
index e51fe28..d9cbe91 100644
--- a/macros.c
+++ b/macros.c
@@ -503,9 +503,15 @@ STREAM         *expandmacro(
             if (macarg == NULL)
                 break;                 /* Don't pick up any more arguments. */
 
+            nextcp = skipwhite (cp);
             arg = new_arg();
             arg->label = memcheck(strdup(macarg->label));       /* Copy the name */
-            arg->value = getstring_macarg(refstr, cp, &nextcp);
+            if (*nextcp != ',') {
+                arg->value = getstring_macarg(refstr, cp, &nextcp);
+            }
+            else {
+                arg->value = NULL;
+            }
             nargs++;                   /* Count nonkeyword arguments only. */
         }
 
@@ -527,9 +533,13 @@ STREAM         *expandmacro(
 
         for (macarg = mac->args; macarg != NULL; macarg = macarg->next) {
             arg = find_arg(args, macarg->label);
-            if (arg == NULL) {
-                arg = new_arg();
-                arg->label = memcheck(strdup(macarg->label));
+            if (arg == NULL || arg->value == NULL) {
+                int wasnull = 0;
+                if (arg == NULL) {
+                    wasnull = 1;
+                    arg = new_arg();
+                    arg->label = memcheck(strdup(macarg->label));
+                }
                 if (macarg->locsym) {
                     char            temp[32];
 
@@ -541,8 +551,10 @@ STREAM         *expandmacro(
                 } else
                     arg->value = memcheck(strdup(""));
 
-                arg->next = args;
-                args = arg;
+                if (wasnull) {
+                    arg->next = args;
+                    args = arg;
+                }
             }
         }
 
diff --git a/tests/test-macro-comma.lst.ok b/tests/test-macro-comma.lst.ok
index 4ef9eba..3789fbe 100644
--- a/tests/test-macro-comma.lst.ok
+++ b/tests/test-macro-comma.lst.ok
@@ -49,7 +49,35 @@
        1                                        ; <bro<ken>
       35 000000                                 braket  <bro<ken> string
        1                                        ; <bro<ken>
-      35                                
+      36                                
+      37                                ;
+      38                                ; Test that commas work with default arguments
+      39                                ;
+      40                                        .macro  tstarg a1,a2=default,a3,a4
+      41                                        .narg   label	; second arg is "a2"
+      42                                        .endm
+      43                                
+      44 000000                         start:  tstarg          ; 0 args
+       1        000000                          .narg   label	; second arg is "default"
+      45 000000                                 tstarg   123    ; 1 arg
+       1        000001                          .narg   label	; second arg is "default"
+      46 000000                                 tstarg   1,     ; 2 args
+       1        000002                          .narg   label	; second arg is ""
+      47 000000                                 tstarg   ,2     ; 2 args
+       1        000002                          .narg   label	; second arg is "2"
+      48 000000                                 tstarg   ,      ; 2 args
+       1        000002                          .narg   label	; second arg is ""
+      49 000000                                 tstarg   ,,     ; 3 args
+       1        000003                          .narg   label	; second arg is "default"
+      50 000000                                 tstarg   1,,    ; 3 args
+       1        000003                          .narg   label	; second arg is "default"
+      51 000000                                 tstarg   ,,3    ; 3 args
+       1        000003                          .narg   label	; second arg is "default"
+      52 000000                                 tstarg   1,,3   ; 3 args
+       1        000003                          .narg   label	; second arg is "default"
+      53 000000                                 tstarg   1,2,3  ; 3 args
+       1        000003                          .narg   label	; second arg is "2"
+      53                                
 
 
 Symbol table
diff --git a/tests/test-macro-comma.mac b/tests/test-macro-comma.mac
index d2783b4..87bd1fc 100644
--- a/tests/test-macro-comma.mac
+++ b/tests/test-macro-comma.mac
@@ -33,3 +33,21 @@ start:  tstarg          ; 0 args
         braket  ^/broken
         braket  <bro<ken>
         braket  <bro<ken> string
+
+;
+; Test that commas work with default arguments
+;
+        .macro  tstarg a1,a2=default,a3,a4
+        .narg   label	; second arg is "a2"
+        .endm
+
+start:  tstarg          ; 0 args
+        tstarg   123    ; 1 arg
+        tstarg   1,     ; 2 args
+        tstarg   ,2     ; 2 args
+        tstarg   ,      ; 2 args
+        tstarg   ,,     ; 3 args
+        tstarg   1,,    ; 3 args
+        tstarg   ,,3    ; 3 args
+        tstarg   1,,3   ; 3 args
+        tstarg   1,2,3  ; 3 args