diff --git a/eval.c b/eval.c
index e5cf0c79..d9a5a0f9 100644
--- a/eval.c
+++ b/eval.c
@@ -204,7 +204,7 @@ static void expand_bcode (sexp ctx, sexp_uint_t size) {
   if (sexp_bytecode_length(sexp_context_bc(ctx))
       < (sexp_context_pos(ctx))+size) {
     tmp=sexp_alloc_bytecode(ctx, sexp_bytecode_length(sexp_context_bc(ctx))*2);
-    sexp_bytecode_name(tmp) = SEXP_FALSE;
+    sexp_bytecode_name(tmp) = sexp_bytecode_name(sexp_context_bc(ctx));
     sexp_bytecode_length(tmp)
       = sexp_bytecode_length(sexp_context_bc(ctx))*2;
     sexp_bytecode_literals(tmp)
@@ -551,6 +551,7 @@ static sexp analyze_lambda (sexp ctx, sexp x) {
       sexp_return(res, sexp_compile_error(ctx, "duplicate parameter", x));
   /* build lambda and analyze body */
   res = sexp_make_lambda(ctx, tmp=sexp_copy_list(ctx, sexp_cadr(x)));
+  sexp_lambda_source(res) = sexp_pair_source(x);
   ctx2 = sexp_make_child_context(ctx, res);
   tmp = sexp_flatten_dot(ctx2, sexp_lambda_params(res));
   sexp_context_env(ctx2) = sexp_extend_env(ctx2, sexp_context_env(ctx2), tmp, res);
@@ -624,6 +625,7 @@ static sexp analyze_define (sexp ctx, sexp x) {
       sexp_push(ctx, sexp_lambda_sv(sexp_env_lambda(env)), name);
       sexp_push(ctx, sexp_lambda_locals(sexp_env_lambda(env)), name);
       tmp = sexp_cons(ctx, sexp_cdr(x), ctx);
+      sexp_pair_source(tmp) = sexp_pair_source(x);
       sexp_push(ctx, sexp_lambda_defs(sexp_env_lambda(env)), tmp);
       res = SEXP_VOID;
     } else {
diff --git a/include/chibi/sexp.h b/include/chibi/sexp.h
index ad773145..e2dc3e8c 100644
--- a/include/chibi/sexp.h
+++ b/include/chibi/sexp.h
@@ -183,6 +183,7 @@ struct sexp_struct {
   char gc_mark;
   unsigned int immutablep:1;
   unsigned int freep:1;
+  unsigned int syntacticp:1;
 #if SEXP_USE_HEADER_MAGIC
   unsigned int magic;
 #endif
@@ -239,12 +240,11 @@ struct sexp_struct {
     } cpointer;
     /* runtime types */
     struct {
-      unsigned int syntacticp:1;
       sexp parent, lambda, bindings;
     } env;
     struct {
       sexp_uint_t length;
-      sexp name, literals;
+      sexp name, literals, source;
       unsigned char data[];
     } bytecode;
     struct {
@@ -271,22 +271,22 @@ struct sexp_struct {
     } core;
     /* ast types */
     struct {
-      sexp name, params, body, defs, locals, flags, fv, sv;
+      sexp name, params, body, defs, locals, flags, fv, sv, source;
     } lambda;
     struct {
-      sexp test, pass, fail;
+      sexp test, pass, fail, source;
     } cnd;
     struct {
-      sexp var, value;
+      sexp var, value, source;
     } set;
     struct {
-      sexp name, cell;
+      sexp name, cell, source;
     } ref;
     struct {
-      sexp ls;
+      sexp ls, source;
     } seq;
     struct {
-      sexp value;
+      sexp value, source;
     } lit;
     /* compiler state */
     struct {
@@ -604,9 +604,10 @@ SEXP_API sexp sexp_make_unsigned_integer(sexp ctx, sexp_luint_t x);
 #define sexp_bytecode_length(x)   ((x)->value.bytecode.length)
 #define sexp_bytecode_name(x)     ((x)->value.bytecode.name)
 #define sexp_bytecode_literals(x) ((x)->value.bytecode.literals)
+#define sexp_bytecode_source(x)   ((x)->value.bytecode.source)
 #define sexp_bytecode_data(x)     ((x)->value.bytecode.data)
 
-#define sexp_env_syntactic_p(x)   ((x)->value.env.syntacticp)
+#define sexp_env_syntactic_p(x)   ((x)->syntacticp)
 #define sexp_env_parent(x)        ((x)->value.env.parent)
 #define sexp_env_bindings(x)      ((x)->value.env.bindings)
 #define sexp_env_local_p(x)       (sexp_env_parent(x))
@@ -648,21 +649,27 @@ SEXP_API sexp sexp_make_unsigned_integer(sexp ctx, sexp_luint_t x);
 #define sexp_lambda_body(x)   ((x)->value.lambda.body)
 #define sexp_lambda_fv(x)     ((x)->value.lambda.fv)
 #define sexp_lambda_sv(x)     ((x)->value.lambda.sv)
+#define sexp_lambda_source(x) ((x)->value.lambda.source)
 
 #define sexp_cnd_test(x)      ((x)->value.cnd.test)
 #define sexp_cnd_pass(x)      ((x)->value.cnd.pass)
 #define sexp_cnd_fail(x)      ((x)->value.cnd.fail)
+#define sexp_cnd_source(x)    ((x)->value.cnd.source)
 
 #define sexp_set_var(x)       ((x)->value.set.var)
 #define sexp_set_value(x)     ((x)->value.set.value)
+#define sexp_set_source(x)    ((x)->value.set.source)
 
 #define sexp_ref_name(x)      ((x)->value.ref.name)
 #define sexp_ref_cell(x)      ((x)->value.ref.cell)
 #define sexp_ref_loc(x)       (sexp_cdr(sexp_ref_cell(x)))
+#define sexp_ref_source(x)    ((x)->value.ref.source)
 
 #define sexp_seq_ls(x)        ((x)->value.seq.ls)
+#define sexp_seq_source(x)    ((x)->value.seq.source)
 
 #define sexp_lit_value(x)     ((x)->value.lit.value)
+#define sexp_lit_source(x)    ((x)->value.lit.source)
 
 #define sexp_stack_length(x)  ((x)->value.stack.length)
 #define sexp_stack_top(x)     ((x)->value.stack.top)
diff --git a/sexp.c b/sexp.c
index 069edea7..a1ff7949 100644
--- a/sexp.c
+++ b/sexp.c
@@ -100,15 +100,15 @@ static struct sexp_struct _sexp_type_specs[] = {
   _DEF_TYPE(SEXP_MACRO, sexp_offsetof(macro, proc), 2, 2, 0, 0, sexp_sizeof(macro), 0, 0, "macro", NULL),
   _DEF_TYPE(SEXP_SYNCLO, sexp_offsetof(synclo, env), 3, 3, 0, 0, sexp_sizeof(synclo), 0, 0, "syntactic-closure", NULL),
   _DEF_TYPE(SEXP_ENV, sexp_offsetof(env, parent), 3, 3, 0, 0, sexp_sizeof(env), 0, 0, "environment", NULL),
-  _DEF_TYPE(SEXP_BYTECODE, sexp_offsetof(bytecode, name), 2, 2, 0, 0, sexp_sizeof(bytecode), offsetof(struct sexp_struct, value.bytecode.length), 1, "bytecode", NULL),
+  _DEF_TYPE(SEXP_BYTECODE, sexp_offsetof(bytecode, name), 3, 3, 0, 0, sexp_sizeof(bytecode), offsetof(struct sexp_struct, value.bytecode.length), 1, "bytecode", NULL),
   _DEF_TYPE(SEXP_CORE, 0, 0, 0, 0, 0, sexp_sizeof(core), 0, 0, "core-form", NULL),
   _DEF_TYPE(SEXP_OPCODE, sexp_offsetof(opcode, data), 3, 3, 0, 0, sexp_sizeof(opcode), 0, 0, "opcode", NULL),
-  _DEF_TYPE(SEXP_LAMBDA, sexp_offsetof(lambda, name), 8, 8, 0, 0, sexp_sizeof(lambda), 0, 0, "lambda", NULL),
-  _DEF_TYPE(SEXP_CND, sexp_offsetof(cnd, test), 3, 3, 0, 0, sexp_sizeof(cnd), 0, 0, "conditional", NULL),
-  _DEF_TYPE(SEXP_REF, sexp_offsetof(ref, name), 2, 2, 0, 0, sexp_sizeof(ref), 0, 0, "reference", NULL),
-  _DEF_TYPE(SEXP_SET, sexp_offsetof(set, var), 2, 2, 0, 0, sexp_sizeof(set), 0, 0, "set!", NULL),
-  _DEF_TYPE(SEXP_SEQ, sexp_offsetof(seq, ls), 1, 1, 0, 0, sexp_sizeof(seq), 0, 0, "sequence", NULL),
-  _DEF_TYPE(SEXP_LIT, sexp_offsetof(lit, value), 1, 1, 0, 0, sexp_sizeof(lit), 0, 0, "literal", NULL),
+  _DEF_TYPE(SEXP_LAMBDA, sexp_offsetof(lambda, name), 9, 9, 0, 0, sexp_sizeof(lambda), 0, 0, "lambda", NULL),
+  _DEF_TYPE(SEXP_CND, sexp_offsetof(cnd, test), 4, 4, 0, 0, sexp_sizeof(cnd), 0, 0, "conditional", NULL),
+  _DEF_TYPE(SEXP_REF, sexp_offsetof(ref, name), 3, 3, 0, 0, sexp_sizeof(ref), 0, 0, "reference", NULL),
+  _DEF_TYPE(SEXP_SET, sexp_offsetof(set, var), 3, 3, 0, 0, sexp_sizeof(set), 0, 0, "set!", NULL),
+  _DEF_TYPE(SEXP_SEQ, sexp_offsetof(seq, ls), 2, 2, 0, 0, sexp_sizeof(seq), 0, 0, "sequence", NULL),
+  _DEF_TYPE(SEXP_LIT, sexp_offsetof(lit, value), 2, 2, 0, 0, sexp_sizeof(lit), 0, 0, "literal", NULL),
   _DEF_TYPE(SEXP_STACK, sexp_offsetof(stack, data), 1, 1, sexp_offsetof(stack, top), 1, sexp_sizeof(stack), offsetof(struct sexp_struct, value.stack.length), sizeof(sexp), "stack", NULL),
   _DEF_TYPE(SEXP_CONTEXT, sexp_offsetof(context, bc), 7, 7, 0, 0, sexp_sizeof(context), 0, 0, "context", NULL),
 };
@@ -417,8 +417,10 @@ sexp sexp_print_exception_op (sexp ctx sexp_api_params(self, n), sexp exn, sexp
         sexp_write_string(ctx, sexp_opcode_name(sexp_exception_procedure(exn)), out);
       }
     }
-    if (sexp_pairp(sexp_exception_source(exn))) {
-      ls = sexp_exception_source(exn);
+    ls = sexp_exception_source(exn);
+    if ((! (ls && sexp_pairp(ls))) && sexp_exception_procedure(exn))
+      ls = sexp_bytecode_source(sexp_procedure_code(sexp_exception_procedure(exn)));
+    if (ls && sexp_pairp(ls)) {
       if (sexp_fixnump(sexp_cdr(ls)) && (sexp_cdr(ls) >= SEXP_ZERO)) {
         sexp_write_string(ctx, " on line ", out);
         sexp_write(ctx, sexp_cdr(ls), out);
diff --git a/vm.c b/vm.c
index 3ae152da..8e96d597 100644
--- a/vm.c
+++ b/vm.c
@@ -301,6 +301,7 @@ static void generate_lambda (sexp ctx, sexp lambda) {
   len = sexp_length(ctx2, sexp_lambda_params(lambda));
   bc = finalize_bytecode(ctx2);
   sexp_bytecode_name(bc) = sexp_lambda_name(lambda);
+  sexp_bytecode_source(bc) = sexp_lambda_source(lambda);
   if (sexp_nullp(fv)) {
     /* shortcut, no free vars */
     tmp = sexp_make_vector(ctx2, SEXP_ZERO, SEXP_VOID);
@@ -441,9 +442,12 @@ static sexp_uint_t sexp_restore_stack (sexp saved, sexp *current) {
       goto call_error_handler;}                                     \
   while (0)
 
-#define sexp_check_exception() do {if (sexp_exceptionp(_ARG1)) \
-                                     goto call_error_handler;} \
-                                while (0)
+#define sexp_check_exception()                                 \
+  do {if (sexp_exceptionp(_ARG1)) {                            \
+      if (! sexp_exception_procedure(_ARG1))                   \
+        sexp_exception_procedure(_ARG1) = self;                \
+      goto call_error_handler;}}                               \
+    while (0)
 
 sexp sexp_vm (sexp ctx, sexp proc) {
   sexp bc = sexp_procedure_code(proc), cp = sexp_procedure_vars(proc);