diff --git a/src/backends/regex.c b/src/backends/regex.c
index b0cfc2b8a812b2bb7724283f2d31171d7e0292b6..12e84f63a71a1491e8ce66bf0e70db8beac7b0ea 100644
--- a/src/backends/regex.c
+++ b/src/backends/regex.c
@@ -294,7 +294,7 @@ void h_rvm_patch_arg(HRVMProg *prog, uint16_t ip, uint16_t new_val) {
 
 size_t h_svm_count_to_mark(HSVMContext *ctx) {
   size_t ctm;
-  for (ctm = 0; ctm < ctx->stack_count-1; ctm++) {
+  for (ctm = 0; ctm < ctx->stack_count; ctm++) {
     if (ctx->stack[ctx->stack_count - 1 - ctm]->token_type == TT_MARK)
       return ctm;
   }
diff --git a/src/backends/regex_debug.c b/src/backends/regex_debug.c
index 78a4099ad310a87a231186f315d07defb7f757ab..8b2ea31163504e59b89c365a26420c1ff48e4a7a 100644
--- a/src/backends/regex_debug.c
+++ b/src/backends/regex_debug.c
@@ -67,12 +67,12 @@ void dump_rvm_prog(HRVMProg *prog) {
       if (high < low)
 	printf("NONE\n");
       else {
-	if (low >= 0x32 && low <= 0x7e)
+	if (low >= 0x20 && low <= 0x7e)
 	  printf("%02hhx ('%c')", low, low);
 	else
 	  printf("%02hhx", low);
 	
-	if (high >= 0x32 && high <= 0x7e)
+	if (high >= 0x20 && high <= 0x7e)
 	  printf(" - %02hhx ('%c')\n", high, high);
 	else
 	  printf(" - %02hhx\n", high);
diff --git a/src/hammer.h b/src/hammer.h
index ebbec52a8fcc4b439d435fb7b79599ccddfc0025..b0fabd115b9cfda3e3d3bd2a66f70d8b4817c45d 100644
--- a/src/hammer.h
+++ b/src/hammer.h
@@ -370,7 +370,7 @@ HAMMER_FN_DECL_NOARG(HParser*, h_nothing_p);
  *
  * Result token type: TT_SEQUENCE
  */
-HAMMER_FN_DECL_VARARGS_ATTR(__attribute__((sentinel)), HParser*, h_sequence, const HParser* p);
+HAMMER_FN_DECL_VARARGS_ATTR(__attribute__((sentinel)), HParser*, h_sequence, HParser* p);
 
 /**
  * Given an array of parsers, p_array, apply each parser in order. The 
@@ -379,7 +379,7 @@ HAMMER_FN_DECL_VARARGS_ATTR(__attribute__((sentinel)), HParser*, h_sequence, con
  *
  * Result token type: The type of the first successful parser's result.
  */
-HAMMER_FN_DECL_VARARGS_ATTR(__attribute__((sentinel)), HParser*, h_choice, const HParser* p);
+HAMMER_FN_DECL_VARARGS_ATTR(__attribute__((sentinel)), HParser*, h_choice, HParser* p);
 
 /**
  * Given two parsers, p1 and p2, this parser succeeds in the following 
diff --git a/src/parsers/charset.c b/src/parsers/charset.c
index a1fe668cf0f71969c872fd780d845ad252768b02..db4c2e777216ce798179bd930d28ea4ad4685cd1 100644
--- a/src/parsers/charset.c
+++ b/src/parsers/charset.c
@@ -56,7 +56,7 @@ static bool cs_ctrvm(HRVMProg *prog, void *env) {
       if (collecting) {
 	collecting = false;
 	uint16_t insn = h_rvm_insert_insn(prog, RVM_FORK, 0);
-	h_rvm_insert_insn(prog, RVM_MATCH, range_start | i << 8);
+	h_rvm_insert_insn(prog, RVM_MATCH, range_start | (i-1) << 8);
 	h_rvm_insert_insn(prog, RVM_GOTO, 0);
 	h_rvm_patch_arg(prog, insn, h_rvm_get_ip(prog));
       }
diff --git a/src/parsers/choice.c b/src/parsers/choice.c
index 5485f2f35cdbee4a0513dab2200bf306255d6550..32c49910ae72360874705541fa07f0737c938c22 100644
--- a/src/parsers/choice.c
+++ b/src/parsers/choice.c
@@ -3,7 +3,7 @@
 
 typedef struct {
   size_t len;
-  const HParser **p_array;
+  HParser **p_array;
 } HSequence;
 
 
@@ -58,16 +58,15 @@ static HCFChoice* desugar_choice(HAllocator *mm__, void *env) {
 static bool choice_ctrvm(HRVMProg *prog, void* env) {
   HSequence *s = (HSequence*)env;
   uint16_t gotos[s->len];
-  uint16_t start = h_rvm_get_ip(prog);
   for (size_t i=0; i<s->len; ++i) {
     uint16_t insn = h_rvm_insert_insn(prog, RVM_FORK, 0);
-    if (!h_compile_regex(prog, s->p_array[i]->env))
+    if (!h_compile_regex(prog, s->p_array[i]))
       return false;
-    gotos[i] = h_rvm_insert_insn(prog, RVM_GOTO, 0);
+    gotos[i] = h_rvm_insert_insn(prog, RVM_GOTO, 65535);
     h_rvm_patch_arg(prog, insn, h_rvm_get_ip(prog));
   }
-  uint16_t jump = h_rvm_insert_insn(prog, RVM_STEP, 0);
-  for (size_t i=start; i<s->len; ++i) {
+  uint16_t jump = h_rvm_get_ip(prog);
+  for (size_t i=0; i<s->len; ++i) {
       h_rvm_patch_arg(prog, gotos[i], jump);
   }
   return true;
@@ -81,7 +80,7 @@ static const HParserVtable choice_vt = {
   .compile_to_rvm = choice_ctrvm,
 };
 
-HParser* h_choice(const HParser* p, ...) {
+HParser* h_choice(HParser* p, ...) {
   va_list ap;
   va_start(ap, p);
   HParser* ret = h_choice__mv(&system_allocator, p,  ap);
@@ -89,7 +88,7 @@ HParser* h_choice(const HParser* p, ...) {
   return ret;
 }
 
-HParser* h_choice__m(HAllocator* mm__, const HParser* p, ...) {
+HParser* h_choice__m(HAllocator* mm__, HParser* p, ...) {
   va_list ap;
   va_start(ap, p);
   HParser* ret = h_choice__mv(mm__, p,  ap);
@@ -97,28 +96,28 @@ HParser* h_choice__m(HAllocator* mm__, const HParser* p, ...) {
   return ret;
 }
 
-HParser* h_choice__v(const HParser* p, va_list ap) {
+HParser* h_choice__v(HParser* p, va_list ap) {
   return h_choice__mv(&system_allocator, p, ap);
 }
 
-HParser* h_choice__mv(HAllocator* mm__, const HParser* p, va_list ap_) {
+HParser* h_choice__mv(HAllocator* mm__, HParser* p, va_list ap_) {
   va_list ap;
   size_t len = 0;
   HSequence *s = h_new(HSequence, 1);
 
-  const HParser *arg;
+  HParser *arg;
   va_copy(ap, ap_);
   do {
     len++;
-    arg = va_arg(ap, const HParser *);
+    arg = va_arg(ap, HParser *);
   } while (arg);
   va_end(ap);
-  s->p_array = h_new(const HParser *, len);
+  s->p_array = h_new(HParser *, len);
 
   va_copy(ap, ap_);
   s->p_array[0] = p;
   for (size_t i = 1; i < len; i++) {
-    s->p_array[i] = va_arg(ap, const HParser *);
+    s->p_array[i] = va_arg(ap, HParser *);
   } while (arg);
   va_end(ap);
 
@@ -139,7 +138,7 @@ HParser* h_choice__ma(HAllocator* mm__, void *args[]) {
   } while(arg);
 
   HSequence *s = h_new(HSequence, 1);
-  s->p_array = h_new(const HParser *, len);
+  s->p_array = h_new(HParser *, len);
 
   for (size_t i = 0; i < len; i++) {
     s->p_array[i] = ((HParser **)args)[i];
diff --git a/src/parsers/ignoreseq.c b/src/parsers/ignoreseq.c
index 3b920f185f6dd7edf4ff18ae4bc588a33129267f..8fcc143b8a4b9a6b2248d9a4de5596560593d58d 100644
--- a/src/parsers/ignoreseq.c
+++ b/src/parsers/ignoreseq.c
@@ -83,7 +83,7 @@ static bool h_svm_action_ignoreseq(HArena *arena, HSVMContext *ctx, void* env) {
   // stack.
   assert(seq->len >= 1);
   for (int i = seq->len - 1; i>=0; i--) {
-    if (i == (int)seq->which && ctx->stack[ctx->stack_count]->token_type != TT_MARK) 
+    if (i == (int)seq->which && ctx->stack[ctx->stack_count-1]->token_type != TT_MARK) 
       save = ctx->stack[ctx->stack_count-1];
     // skip over everything up to and including the mark.
     while (ctx->stack[--ctx->stack_count]->token_type != TT_MARK)
diff --git a/src/parsers/sequence.c b/src/parsers/sequence.c
index 4de218339bde91d72918bc1d7b1dedfee681197c..27a667a6cd0229884277744aefeca848745315fd 100644
--- a/src/parsers/sequence.c
+++ b/src/parsers/sequence.c
@@ -4,7 +4,7 @@
 
 typedef struct {
   size_t len;
-  const HParser **p_array;
+  HParser **p_array;
 } HSequence;
 
 static HParseResult* parse_sequence(void *env, HParseState *state) {
@@ -86,7 +86,7 @@ static bool sequence_ctrvm(HRVMProg *prog, void *env) {
   HSequence *s = (HSequence*)env;
   h_rvm_insert_insn(prog, RVM_PUSH, 0);
   for (size_t i=0; i<s->len; ++i) {
-    if (!s->p_array[i]->vtable->compile_to_rvm(prog, s->p_array[i]->env))
+    if (!s->p_array[i]->vtable->compile_to_rvm(prog, s->p_array[i]))
       return false;
   }
   h_rvm_insert_insn(prog, RVM_ACTION, h_rvm_create_action(prog, h_svm_action_make_sequence, NULL));
@@ -101,7 +101,7 @@ static const HParserVtable sequence_vt = {
   .compile_to_rvm = sequence_ctrvm,
 };
 
-HParser* h_sequence(const HParser* p, ...) {
+HParser* h_sequence(HParser* p, ...) {
   va_list ap;
   va_start(ap, p);
   HParser* ret = h_sequence__mv(&system_allocator, p,  ap);
@@ -109,7 +109,7 @@ HParser* h_sequence(const HParser* p, ...) {
   return ret;
 }
 
-HParser* h_sequence__m(HAllocator* mm__, const HParser* p, ...) {
+HParser* h_sequence__m(HAllocator* mm__, HParser* p, ...) {
   va_list ap;
   va_start(ap, p);
   HParser* ret = h_sequence__mv(mm__, p,  ap);
@@ -117,27 +117,27 @@ HParser* h_sequence__m(HAllocator* mm__, const HParser* p, ...) {
   return ret;
 }
 
-HParser* h_sequence__v(const HParser* p, va_list ap) {
+HParser* h_sequence__v(HParser* p, va_list ap) {
   return h_sequence__mv(&system_allocator, p, ap);
 }
 
-HParser* h_sequence__mv(HAllocator* mm__, const HParser *p, va_list ap_) {
+HParser* h_sequence__mv(HAllocator* mm__, HParser *p, va_list ap_) {
   va_list ap;
   size_t len = 0;
   const HParser *arg;
   va_copy(ap, ap_);
   do {
     len++;
-    arg = va_arg(ap, const HParser *);
+    arg = va_arg(ap, HParser *);
   } while (arg);
   va_end(ap);
   HSequence *s = h_new(HSequence, 1);
-  s->p_array = h_new(const HParser *, len);
+  s->p_array = h_new(HParser *, len);
 
   va_copy(ap, ap_);
   s->p_array[0] = p;
   for (size_t i = 1; i < len; i++) {
-    s->p_array[i] = va_arg(ap, const HParser *);
+    s->p_array[i] = va_arg(ap, HParser *);
   } while (arg);
   va_end(ap);
 
@@ -158,7 +158,7 @@ HParser* h_sequence__ma(HAllocator* mm__, void *args[]) {
   } while(arg);
   
   HSequence *s = h_new(HSequence, 1);
-  s->p_array = h_new(const HParser *, len);
+  s->p_array = h_new(HParser *, len);
 
   for (size_t i = 0; i < len; i++) {
     s->p_array[i] = ((HParser **)args)[i];