diff --git a/runtime.c b/runtime.c
index b7a9a9b7..6c6fa9b0 100644
--- a/runtime.c
+++ b/runtime.c
@@ -71,12 +71,20 @@ static symbol_type Cyc_void_symbol = {symbol_tag, "", nil};
 const object quote_void = &Cyc_void_symbol;
 
 /* Stack Traces */
-const int MAX_STACK_TRACES = 10;
-char **Cyc_Stack_Traces;
-int Cyc_Stack_Trace_Idx = 0;
+static const int MAX_STACK_TRACES = 10;
+static char **Cyc_Stack_Traces;
+static int Cyc_Stack_Trace_Idx = 0;
+
+void Cyc_st_init() { 
+  Cyc_Stack_Traces = calloc(MAX_STACK_TRACES, sizeof(char *));
+}
+
+void Cyc_st_add(char *frame) { 
+  /* add to circ buf */ 
+  Cyc_Stack_Traces[Cyc_Stack_Trace_Idx] = frame;
+  Cyc_Stack_Trace_Idx = (Cyc_Stack_Trace_Idx + 1) % MAX_STACK_TRACES;
+}
 
-void Cyc_st_init() { /* calloc tbl */ }
-void Cyc_st_add(char *frame) { /* add to circ buf */ }
 void Cyc_st_print(FILE *out) {
   /* print to stream, note it is possible that
      some traces could be on the stack after a GC.
@@ -85,6 +93,13 @@ void Cyc_st_print(FILE *out) {
      or, with the tbl being so small, maybe it will
      not be an issue in practice? a bit risky to ignore though
   */
+  int i = (Cyc_Stack_Trace_Idx + 1) % MAX_STACK_TRACES;
+  while (i != Cyc_Stack_Trace_Idx) {
+    if (Cyc_Stack_Traces[i]) {
+      fprintf(out, "%s\n", Cyc_Stack_Traces[i]);
+    }
+    i = (i + 1) % MAX_STACK_TRACES;
+  }
 }
 /* END Stack Traces section */
 
diff --git a/runtime.h b/runtime.h
index 6826fcd6..bd772ee3 100644
--- a/runtime.h
+++ b/runtime.h
@@ -156,6 +156,10 @@ object memqp(object,list);
 char *transport(char *,int);
 void GC(closure,object*,int) never_returns;
 
+void Cyc_st_init();
+void Cyc_st_add(char *frame);
+void Cyc_st_print(FILE *out);
+
 char *_strdup (const char *s);
 object add_symbol(symbol_type *psym);
 object add_symbol_by_name(const char *name);