diff --git a/src/system/boot/loader/heap.cpp b/src/system/boot/loader/heap.cpp
index cce03ef1f7..644ee3d2bc 100644
--- a/src/system/boot/loader/heap.cpp
+++ b/src/system/boot/loader/heap.cpp
@@ -52,6 +52,9 @@
 
 const static size_t kAlignment = 8;
 	// all memory chunks will be a multiple of this
+
+const static size_t kDefaultHeapSize = (1024 + 256) * 1024;
+	// default initial heap size, unless overridden by platform loader
 const static size_t kLargeAllocationThreshold = 16 * 1024;
 	// allocations of this size or larger are allocated via
 	// platform_allocate_region()
@@ -401,6 +404,9 @@ heap_print_statistics()
 status_t
 heap_init(stage2_args* args)
 {
+	if (args->heap_size == 0)
+		args->heap_size = kDefaultHeapSize;
+
 	void* base;
 	void* top;
 	if (platform_init_heap(args, &base, &top) < B_OK)
diff --git a/src/system/boot/platform/amiga_m68k/start.cpp b/src/system/boot/platform/amiga_m68k/start.cpp
index 8881ca7209..f0c50f6ad1 100644
--- a/src/system/boot/platform/amiga_m68k/start.cpp
+++ b/src/system/boot/platform/amiga_m68k/start.cpp
@@ -20,8 +20,6 @@
 #include "rom_calls.h"
 
 
-#define HEAP_SIZE 65536
-
 // GCC defined globals
 extern void (*__ctor_list)(void);
 extern void (*__ctor_end)(void);
@@ -132,7 +130,7 @@ _start(void)
 	call_ctors();
 		// call C++ constructors before doing anything else
 
-	args.heap_size = HEAP_SIZE;
+	args.heap_size = 0;
 	args.arguments = NULL;
 	
 	//serial_init();
diff --git a/src/system/boot/platform/atari_m68k/start.cpp b/src/system/boot/platform/atari_m68k/start.cpp
index c0f6503bcc..381f0d9431 100644
--- a/src/system/boot/platform/atari_m68k/start.cpp
+++ b/src/system/boot/platform/atari_m68k/start.cpp
@@ -20,8 +20,6 @@
 #include "toscalls.h"
 
 
-#define HEAP_SIZE 65536
-
 // GCC defined globals
 extern void (*__ctor_list)(void);
 extern void (*__ctor_end)(void);
@@ -140,7 +138,7 @@ _start(void)
 		// call C++ constructors before doing anything else
 	Bconout(DEV_CON, 'I');
 
-	args.heap_size = HEAP_SIZE;
+	args.heap_size = 0;
 	args.arguments = NULL;
 	
 	// so we can dprintf
diff --git a/src/system/boot/platform/bios_ia32/start.cpp b/src/system/boot/platform/bios_ia32/start.cpp
index 89c870a1d2..152f7a4b0f 100644
--- a/src/system/boot/platform/bios_ia32/start.cpp
+++ b/src/system/boot/platform/bios_ia32/start.cpp
@@ -31,9 +31,6 @@
 #include "smp.h"
 
 
-#define HEAP_SIZE ((1024 + 256) * 1024)
-
-
 // GCC defined globals
 extern void (*__ctor_list)(void);
 extern void (*__ctor_end)(void);
@@ -184,7 +181,7 @@ _start(void)
 	call_ctors();
 		// call C++ constructors before doing anything else
 
-	args.heap_size = HEAP_SIZE;
+	args.heap_size = 0;
 	args.arguments = NULL;
 
 	serial_init();
diff --git a/src/system/boot/platform/efi/start.cpp b/src/system/boot/platform/efi/start.cpp
index fefead9327..2ccb802f46 100644
--- a/src/system/boot/platform/efi/start.cpp
+++ b/src/system/boot/platform/efi/start.cpp
@@ -233,7 +233,6 @@ extern "C" efi_status
 efi_main(efi_handle image, efi_system_table *systemTable)
 {
 	stage2_args args;
-
 	memset(&args, 0, sizeof(stage2_args));
 
 	kImage = image;
diff --git a/src/system/boot/platform/next_m68k/start.cpp b/src/system/boot/platform/next_m68k/start.cpp
index a69a32903c..df5bd9e8d5 100644
--- a/src/system/boot/platform/next_m68k/start.cpp
+++ b/src/system/boot/platform/next_m68k/start.cpp
@@ -19,7 +19,6 @@
 #include "keyboard.h"
 #include "nextrom.h"
 
-#define HEAP_SIZE 65536
 
 // GCC defined globals
 extern void (*__ctor_list)(void);
@@ -246,7 +245,7 @@ start_next(const char *boot_args, struct mon_global *monitor)
 		// call C++ constructors before doing anything else
 	mg->mg_putc('I');
 
-	args.heap_size = HEAP_SIZE;
+	args.heap_size = 0;
 	args.arguments = NULL;
 
 	//serial_init();
diff --git a/src/system/boot/platform/openfirmware/start.cpp b/src/system/boot/platform/openfirmware/start.cpp
index c854e1863a..6e62dc6025 100644
--- a/src/system/boot/platform/openfirmware/start.cpp
+++ b/src/system/boot/platform/openfirmware/start.cpp
@@ -23,9 +23,6 @@
 #include "real_time_clock.h"
 
 
-#define HEAP_SIZE (512 * 1024)
-
-
 // GCC defined globals
 extern void (*__ctor_list)(void);
 extern void (*__ctor_end)(void);
@@ -104,7 +101,7 @@ start(void *openFirmwareEntry)
 
 	// stage2 args - might be set via the command line one day
 	stage2_args args;
-	args.heap_size = HEAP_SIZE;
+	args.heap_size = 0;
 	args.arguments = NULL;
 
 	if (of_init((intptr_t (*)(void*))openFirmwareEntry) != B_OK)
diff --git a/src/system/boot/platform/riscv/start.cpp b/src/system/boot/platform/riscv/start.cpp
index acd0ccd935..669a3ca9bb 100644
--- a/src/system/boot/platform/riscv/start.cpp
+++ b/src/system/boot/platform/riscv/start.cpp
@@ -24,8 +24,6 @@
 #include "graphics.h"
 
 
-#define HEAP_SIZE (1024*1024)
-
 // GCC defined globals
 extern void (*__ctor_list)(void);
 extern void (*__ctor_end)(void);
@@ -205,7 +203,7 @@ _start(int hartId, void* fdt)
 	call_ctors();
 
 	stage2_args args;
-	args.heap_size = HEAP_SIZE;
+	args.heap_size = 0;
 	args.arguments = NULL;
 
 	traps_init();
diff --git a/src/system/boot/platform/u-boot/start.cpp b/src/system/boot/platform/u-boot/start.cpp
index d7d38045a4..8a4a15e689 100644
--- a/src/system/boot/platform/u-boot/start.cpp
+++ b/src/system/boot/platform/u-boot/start.cpp
@@ -30,9 +30,6 @@ extern "C" {
 };
 
 
-#define HEAP_SIZE (128 * 1024)
-
-
 typedef struct uboot_gd {
 	// those are the only few members that we can trust
 	// others depend on compile-time config
@@ -191,7 +188,7 @@ start_gen(int argc, const char **argv, struct image_header *uimage, void *fdt)
 	clear_bss();
 		// call C++ constructors before doing anything else
 	call_ctors();
-	args.heap_size = HEAP_SIZE;
+	args.heap_size = 0;
 	args.arguments = NULL;
 	args.arguments_count = 0;
 	args.platform.boot_tgz_data = NULL;