diff --git a/src/system/boot/arch/arm/arch_mmu.cpp b/src/system/boot/arch/arm/arch_mmu.cpp
index 1183551384..8867f7f753 100644
--- a/src/system/boot/arch/arm/arch_mmu.cpp
+++ b/src/system/boot/arch/arm/arch_mmu.cpp
@@ -474,8 +474,8 @@ mmu_allocate(void *virtualAddress, size_t size)
 		addr_t address = (addr_t)virtualAddress;
 
 		// is the address within the valid range?
-		if (address < KERNEL_BASE
-			|| address + size >= KERNEL_BASE + kMaxKernelSize) {
+		if (address < KERNEL_BASE || address + size * B_PAGE_SIZE
+			>= KERNEL_BASE + kMaxKernelSize) {
 			TRACE(("mmu_allocate in illegal range\n address: %" B_PRIx32
 				"  KERNELBASE: %" B_PRIx32 " KERNEL_BASE + kMaxKernelSize: %"
 				B_PRIx32 "  address + size : %" B_PRIx32 "\n", (uint32)address,
diff --git a/src/system/boot/arch/m68k/mmu.cpp b/src/system/boot/arch/m68k/mmu.cpp
index b7c2526d4a..1a447901d5 100644
--- a/src/system/boot/arch/m68k/mmu.cpp
+++ b/src/system/boot/arch/m68k/mmu.cpp
@@ -338,7 +338,8 @@ mmu_allocate(void *virtualAddress, size_t size)
 		addr_t address = (addr_t)virtualAddress;
 
 		// is the address within the valid range?
-		if (address < KERNEL_BASE || address + size >= KERNEL_BASE + kMaxKernelSize)
+		if (address < KERNEL_BASE || address + size * B_PAGE_SIZE
+			>= KERNEL_BASE + kMaxKernelSize)
 			return NULL;
 
 		for (uint32 i = 0; i < size; i++) {
diff --git a/src/system/boot/platform/amiga_m68k/mmu.cpp b/src/system/boot/platform/amiga_m68k/mmu.cpp
index 03f56b9f4e..1dde414257 100644
--- a/src/system/boot/platform/amiga_m68k/mmu.cpp
+++ b/src/system/boot/platform/amiga_m68k/mmu.cpp
@@ -338,7 +338,8 @@ mmu_allocate(void *virtualAddress, size_t size)
 		addr_t address = (addr_t)virtualAddress;
 
 		// is the address within the valid range?
-		if (address < KERNEL_BASE || address + size >= KERNEL_BASE + kMaxKernelSize)
+		if (address < KERNEL_BASE || address + size * B_PAGE_SIZE
+			>= KERNEL_BASE + kMaxKernelSize)
 			return NULL;
 
 		for (uint32 i = 0; i < size; i++) {
diff --git a/src/system/boot/platform/atari_m68k/mmu.cpp b/src/system/boot/platform/atari_m68k/mmu.cpp
index 7132119fd2..548d6d5c55 100644
--- a/src/system/boot/platform/atari_m68k/mmu.cpp
+++ b/src/system/boot/platform/atari_m68k/mmu.cpp
@@ -339,7 +339,8 @@ mmu_allocate(void *virtualAddress, size_t size)
 		addr_t address = (addr_t)virtualAddress;
 
 		// is the address within the valid range?
-		if (address < KERNEL_BASE || address + size >= KERNEL_BASE + kMaxKernelSize)
+		if (address < KERNEL_BASE || address + size * B_PAGE_SIZE
+			>= KERNEL_BASE + kMaxKernelSize)
 			return NULL;
 
 		for (uint32 i = 0; i < size; i++) {
diff --git a/src/system/boot/platform/bios_ia32/mmu.cpp b/src/system/boot/platform/bios_ia32/mmu.cpp
index 4eef5defa5..93eaed5423 100644
--- a/src/system/boot/platform/bios_ia32/mmu.cpp
+++ b/src/system/boot/platform/bios_ia32/mmu.cpp
@@ -397,8 +397,8 @@ mmu_allocate(void *virtualAddress, size_t size)
 		addr_t address = (addr_t)virtualAddress;
 
 		// is the address within the valid range?
-		if (address < KERNEL_LOAD_BASE
-			|| address + size >= KERNEL_LOAD_BASE + kMaxKernelSize)
+		if (address < KERNEL_LOAD_BASE || address + size * B_PAGE_SIZE
+			>= KERNEL_LOAD_BASE + kMaxKernelSize)
 			return NULL;
 
 		for (uint32 i = 0; i < size; i++) {