diff --git a/build/jam/ArchitectureRules b/build/jam/ArchitectureRules
index d391b638a5..f79ee3e0eb 100644
--- a/build/jam/ArchitectureRules
+++ b/build/jam/ArchitectureRules
@@ -377,6 +377,7 @@ rule KernelArchitectureSetup architecture
 	# Common boot-related cflags which apply to all loaders
 	HAIKU_BOOT_CCFLAGS = $(HAIKU_CCFLAGS_$(architecture)) $(ccBaseFlags) ;
 	HAIKU_BOOT_C++FLAGS = $(HAIKU_C++FLAGS_$(architecture)) $(c++BaseFlags) ;
+	HAIKU_BOOT_OPTIM = -Os ;
 	HAIKU_BOOT_LINKFLAGS = ;
 	HAIKU_BOOT_LDFLAGS = -Bstatic ;
 
diff --git a/build/jam/BootRules b/build/jam/BootRules
index edbabcfafa..468fb240f5 100644
--- a/build/jam/BootRules
+++ b/build/jam/BootRules
@@ -97,6 +97,7 @@ rule SetupBoot
 		ObjectC++Flags $(object) : $(HAIKU_BOOT_C++FLAGS) $(HAIKU_BOOT_$(platform)_C++FLAGS) $(2) ;
 		ObjectDefines $(object) : $(TARGET_KERNEL_DEFINES) ;
 		ASFLAGS on $(object) = $(HAIKU_BOOT_CCFLAGS) $(HAIKU_BOOT_$(platform)_CCFLAGS) ;
+		OPTIM on $(object) = $(HAIKU_BOOT_OPTIM) ;
 
 		# override regular CCFLAGS/C++FLAGS, as we don't want them
 		TARGET_CCFLAGS_$(TARGET_KERNEL_ARCH) on $(object) = ;