diff --git a/scheme/last-revision b/scheme/last-revision
index 3c8cfd3..74d36ca 100644
--- a/scheme/last-revision
+++ b/scheme/last-revision
@@ -1 +1 @@
-1602
+1603
diff --git a/src/ikarus-collect.c b/src/ikarus-collect.c
index 945c06d..cc181a0 100644
--- a/src/ikarus-collect.c
+++ b/src/ikarus-collect.c
@@ -795,16 +795,17 @@ add_code_entry(gc_t* gc, ikptr entry){
 
 static void collect_stack(gc_t* gc, ikptr top, ikptr end){
   if(DEBUG_STACK){
-    fprintf(stderr, "collecting stack from 0x%016lx .. 0x%016lx\n", 
-        (long) top, (long) end);
+    fprintf(stderr, "collecting stack (size=%ld) from 0x%016lx .. 0x%016lx\n", 
+        (long)end - (long)top, (long) top, (long) end);
   }
   while(top < end){
     if(DEBUG_STACK){
-      fprintf(stderr, "collecting frame at 0x%016lx: ", (long) top);
+      fprintf(stderr, "collecting frame at 0x%016lx: \n", (long) top);
     }
     ikptr rp = ref(top, 0);
     long int rp_offset = unfix(ref(rp, disp_frame_offset));
     if(DEBUG_STACK){
+      fprintf(stderr, "rp=0x%016lx\n", rp);
       fprintf(stderr, "rp_offset=%ld\n", rp_offset);
     }
     if(rp_offset <= 0){
diff --git a/src/ikarus-ffi.c b/src/ikarus-ffi.c
index 694174a..7eaac5e 100644
--- a/src/ikarus-ffi.c
+++ b/src/ikarus-ffi.c
@@ -128,10 +128,23 @@ ikrt_ffi_prep_cif(ikptr rtptr, ikptr argstptr, ikpcb* pcb) {
   }
 }
 
-/* FIXME: handle stack overflow */
 
         
+static void
+dump_stack(ikpcb* pcb, char* msg) {
+  fprintf(stderr, "====================  %s\n", msg);
+  ikptr frame_base = pcb->frame_base;
+  ikptr frame_pointer = pcb->frame_pointer;
+  ikptr p = frame_pointer;
+  fprintf(stderr, "fp=0x%016lx   base=0x%016lx\n", frame_pointer, frame_base);
+  while(p < frame_base) {
+    fprintf(stderr, "*0x%016lx = 0x%016lx\n", p, ref(p, 0));
+    p += wordsize;
+  }
+}
 
+
+/* FIXME: handle stack overflow */
 ikptr
 ikrt_seal_scheme_stack(ikpcb* pcb) {
   #if 0
@@ -155,6 +168,7 @@ ikrt_seal_scheme_stack(ikpcb* pcb) {
   ikptr frame_base = pcb->frame_base;
   ikptr frame_pointer = pcb->frame_pointer;
 #ifdef DEBUG_FFI
+  dump_stack(pcb, "BEFORE SEALING");
   fprintf(stderr, "old base=0x%016lx  fp=0x%016lx\n", pcb->frame_base,
       pcb->frame_pointer);
 #endif
@@ -162,7 +176,7 @@ ikrt_seal_scheme_stack(ikpcb* pcb) {
     ikptr underflow_handler = ref(frame_base, -wordsize);
     cont* k = (cont*) pcb->next_k;
     cont* nk = (cont*) ik_unsafe_alloc(pcb, sizeof(cont));
-    nk->tag = k->tag;
+    nk->tag = continuation_tag;
     nk->next = (ikptr) k;
     nk->top = frame_pointer;
 #ifdef DEBUG_FFI
@@ -175,7 +189,7 @@ ikrt_seal_scheme_stack(ikpcb* pcb) {
 #endif
     pcb->next_k = vector_tag + (ikptr)nk;
     pcb->frame_base = frame_pointer;
-    pcb->frame_pointer = frame_pointer - wordsize;
+    pcb->frame_pointer = pcb->frame_base - wordsize;
 #ifdef DEBUG_FFI
     fprintf(stderr, "new base=0x%016lx  fp=0x%016lx\n", pcb->frame_base,
         pcb->frame_pointer);
@@ -187,12 +201,16 @@ ikrt_seal_scheme_stack(ikpcb* pcb) {
     fprintf(stderr, "already sealed\n");
 #endif
   }
+#ifdef DEBUG_FFI
+  dump_stack(pcb, "AFTER SEALING");
+#endif
   return void_object;
 }
 
 ikptr
 ikrt_call_back(ikptr proc, ikpcb* pcb) {
   ikrt_seal_scheme_stack(pcb);
+
   ikptr old_k = pcb->next_k;
   pcb->next_k = 0;
   ikptr entry_point = ref(proc, off_closure_code);
@@ -201,13 +219,13 @@ ikrt_call_back(ikptr proc, ikpcb* pcb) {
   fprintf(stderr, "system_stack = 0x%016lx\n", pcb->system_stack);
 #endif
   ikptr code_ptr = entry_point - off_code_data;
+  pcb->frame_pointer = pcb->frame_base;
   ikptr rv = ik_exec_code(pcb, code_ptr, 0, proc); 
 #ifdef DEBUG_FFI
   fprintf(stderr, "system_stack = 0x%016lx\n", pcb->system_stack);
 #endif
-  ikptr rv2 = ref(pcb->frame_pointer, -2*wordsize);
 #ifdef DEBUG_FFI
-  fprintf(stderr, "rv=0x%016lx   0x%016lx\n", rv, rv2);
+  fprintf(stderr, "rv=0x%016lx\n", rv);
 #endif
   pcb->next_k = old_k;
   pcb->frame_pointer = pcb->frame_base - wordsize;
@@ -215,7 +233,7 @@ ikrt_call_back(ikptr proc, ikpcb* pcb) {
   fprintf(stderr, "rp=0x%016lx\n", ref(pcb->frame_pointer, 0));
 #endif
   pcb->system_stack = system_stack;
-  return rv2;
+  return rv;
 }
 
 
@@ -224,6 +242,9 @@ ikptr
 ikrt_ffi_call(ikptr data, ikptr argsvec, ikpcb* pcb)  {
 
   ikrt_seal_scheme_stack(pcb);
+  ikptr old_k = pcb->next_k;
+  pcb->next_k = 0;
+  ikptr system_stack = pcb->system_stack;
 
   ikptr cifptr  = ref(data, off_vector_data + 0 * wordsize);
   ikptr funptr  = ref(data, off_vector_data + 1 * wordsize);
@@ -247,12 +268,13 @@ ikrt_ffi_call(ikptr data, ikptr argsvec, ikpcb* pcb)  {
     free(avalues[i]);
   }
 #ifdef DEBUG_FFI
-  fprintf(stderr, "DONE WITH CALL, RV=0x%016lx 0x%016lx\n", 
-      (long)val,
-      ref(pcb->frame_pointer, -2*wordsize));
+  fprintf(stderr, "DONE WITH CALL, RV=0x%016lx\n", (long)val);
 #endif
   free(avalues);
   free(rvalue);
+  pcb->frame_pointer = pcb->frame_base - wordsize;
+  pcb->next_k = old_k;
+  pcb->system_stack = system_stack;
   return val;
 }
 
@@ -300,20 +322,22 @@ generic_callback(ffi_cif *cif, void *ret, void **args, void *user_data){
   ikptr code_ptr = code_entry - off_code_data;
   ikptr frame_pointer = pcb->frame_pointer;
   ikptr frame_base = pcb->frame_base;
+  /*
   if ((frame_base - wordsize) != frame_pointer) {
     fprintf(stderr, "ikarus internal error: INVALID FRAME LAYOUT 0x%016lx .. 0x%016lx\n", 
         frame_base, frame_pointer);
     exit(-1);
   }
-  ref(frame_pointer, -2*wordsize) = fix(*((int*)args[0]));
+  */
+  pcb->frame_pointer = pcb->frame_base;
+  ref(pcb->frame_pointer, -2*wordsize) = fix(*((int*)args[0]));
   ikptr rv = ik_exec_code(pcb, code_ptr, fix(-1), proc); 
-  ikptr rv2 = ref(pcb->frame_pointer, -2*wordsize);
 #ifdef DEBUG_FFI
-  fprintf(stderr, "and back with rv=0x%016lx  0x%016lx!\n", rv, rv2);
+  fprintf(stderr, "and back with rv=0x%016lx!\n", rv);
 #endif
   pcb->system_stack = old_system_stack;
   pcb->next_k = old_next_k;
-  *((ikptr*)ret) = unfix(rv2);
+  *((ikptr*)ret) = unfix(rv);
   return;
 }