diff --git a/native/cards.c b/native/cards.c
index 7fbcc30ff8..850e74c6a1 100644
--- a/native/cards.c
+++ b/native/cards.c
@@ -61,6 +61,6 @@ void clear_cards(CELL from, CELL to)
 void collect_cards(CELL gen)
 {
 	int i;
-	for(i = gen + 1; i < gc_generations; i++)
+	for(i = gen + 1; i < gen_count; i++)
 		collect_gen_cards(i);
 }
diff --git a/native/debug.c b/native/debug.c
index 47839b5a03..674eb1c6ec 100644
--- a/native/debug.c
+++ b/native/debug.c
@@ -203,7 +203,7 @@ void dump_generation(ZONE *z)
 void dump_generations(void)
 {
 	int i;
-	for(i = 0; i < gc_generations; i++)
+	for(i = 0; i < gen_count; i++)
 	{
 		fprintf(stderr,"Generation %d: ",i);
 		dump_generation(&generations[i]);
diff --git a/native/factor.c b/native/factor.c
index e01edc3dab..44197b90b5 100644
--- a/native/factor.c
+++ b/native/factor.c
@@ -1,14 +1,14 @@
 #include "factor.h"
 
 void init_factor(char* image, CELL ds_size, CELL cs_size,
-	CELL generations,
+	CELL gen_count,
 	CELL young_size, CELL aging_size,
 	CELL code_size, CELL literal_size)
 {
 	/* initialize random number generator */
 	srand((unsigned)time(NULL));
 	init_ffi();
-	init_arena(generations,young_size,aging_size);
+	init_arena(gen_count,young_size,aging_size);
 	init_compiler(code_size);
 	load_image(image,literal_size);
 	init_stacks(ds_size,cs_size);
@@ -17,7 +17,7 @@ void init_factor(char* image, CELL ds_size, CELL cs_size,
 	init_errors();
 	userenv[CPU_ENV] = tag_object(from_c_string(FACTOR_CPU_STRING));
 	userenv[OS_ENV] = tag_object(from_c_string(FACTOR_OS_STRING));
-	userenv[GEN_ENV] = tag_fixnum(gc_generations);
+	userenv[GEN_ENV] = tag_fixnum(gen_count);
 	userenv[CARD_OFF_ENV] = tag_cell(cards_offset);
 }
 
diff --git a/native/gc.c b/native/gc.c
index 91640c497f..891aceee05 100644
--- a/native/gc.c
+++ b/native/gc.c
@@ -19,17 +19,20 @@ there are two reasons for this:
 - the nursery grows into the guard page, so allot() does not have to
 check for out of memory, whereas allot_zone() (used by the GC) longjmp()s
 back to collecting a higher generation */
-void init_arena(CELL gen_count, CELL young_size, CELL aging_size)
+void init_arena(CELL gens, CELL young_size, CELL aging_size)
 {
 	int i;
 	CELL alloter;
 
-	CELL total_size = (gc_generations - 1) * young_size + 2 * aging_size;
+	CELL total_size = (gens - 1) * young_size + 2 * aging_size;
 	CELL cards_size = total_size / CARD_SIZE;
 
-	gc_generations = gen_count;
+	gen_count = gens;
 	generations = malloc(sizeof(ZONE) * gen_count);
 
+	if(generations == 0)
+		fatal_error("Cannot allocate zone head array",0);
+
 	heap_start = (CELL)alloc_guarded(total_size);
 	heap_end = heap_start + total_size;
 
@@ -40,12 +43,12 @@ void init_arena(CELL gen_count, CELL young_size, CELL aging_size)
 	alloter = heap_start;
 
 	if(heap_start == 0)
-		fatal_error("Cannot allocate data heap",total_size);
+		fatal_error("Cannot allocate data heap",0);
 
 	alloter = init_zone(&tenured,aging_size,alloter);
 	alloter = init_zone(&prior,aging_size,alloter);
 
-	for(i = gc_generations - 2; i >= 0; i--)
+	for(i = gen_count - 2; i >= 0; i--)
 		alloter = init_zone(&generations[i],young_size,alloter);
 
 	clear_cards(NURSERY,TENURED);
diff --git a/native/gc.h b/native/gc.h
index 7814e8d463..75f4d18824 100644
--- a/native/gc.h
+++ b/native/gc.h
@@ -11,12 +11,12 @@ typedef struct {
 } ZONE;
 
 /* total number of generations. */
-CELL gc_generations;
+CELL gen_count;
 
 /* the 0th generation is where new objects are allocated. */
 #define NURSERY 0
 /* the oldest generation */
-#define TENURED (gc_generations-1)
+#define TENURED (gen_count-1)
 
 ZONE *generations;
 
diff --git a/native/memory.c b/native/memory.c
index a5d4617e95..cde16bb442 100644
--- a/native/memory.c
+++ b/native/memory.c
@@ -146,7 +146,7 @@ void primitive_room(void)
 	box_signed_cell(compiling.limit - compiling.base);
 	box_signed_cell(cards_end - cards);
 	box_signed_cell(prior.limit - prior.base);
-	for(gen = gc_generations - 1; gen >= 0; gen--)
+	for(gen = gen_count - 1; gen >= 0; gen--)
 	{
 		ZONE *z = &generations[gen];
 		list = cons(cons(
diff --git a/native/run.h b/native/run.h
index 2e61967f08..c8041d5b37 100644
--- a/native/run.h
+++ b/native/run.h
@@ -14,7 +14,7 @@
 #define ERROR_ENV      12 /* a marker consed onto kernel errors */
 #define IN_ENV         13
 #define OUT_ENV        14
-#define GEN_ENV        15 /* set to gc_generations */
+#define GEN_ENV        15 /* set to gen_count */
 
 /* TAGGED user environment data; see getenv/setenv prims */
 DLLEXPORT CELL userenv[USER_ENV];