diff --git a/include/kernel-defaults.mk b/include/kernel-defaults.mk
index eb852a04cab..70e3f3f5946 100644
--- a/include/kernel-defaults.mk
+++ b/include/kernel-defaults.mk
@@ -45,31 +45,21 @@ else
 endif
 
 ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),y)
-  ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE),y)
+  ifeq ($(strip $(CONFIG_EXTERNAL_CPIO)),"")
     define Kernel/SetInitramfs/PreConfigure
-	{ \
-		grep -v -e CONFIG_BLK_DEV_INITRD $(2)/.config.old > $(2)/.config; \
-		echo 'CONFIG_BLK_DEV_INITRD=y' >> $(2)/.config; \
-		echo 'CONFIG_INITRAMFS_SOURCE=""' >> $(2)/.config; \
-	}
-    endef
-  else
-    ifeq ($(strip $(CONFIG_EXTERNAL_CPIO)),"")
-      define Kernel/SetInitramfs/PreConfigure
 	{ \
 		grep -v -e INITRAMFS -e CONFIG_RD_ -e CONFIG_BLK_DEV_INITRD $(2)/.config.old > $(2)/.config; \
 		echo 'CONFIG_BLK_DEV_INITRD=y' >> $(2)/.config; \
 		echo 'CONFIG_INITRAMFS_SOURCE="$(strip $(1) $(INITRAMFS_EXTRA_FILES))"' >> $(2)/.config; \
 	}
-      endef
-    else
-      define Kernel/SetInitramfs/PreConfigure
+    endef
+  else
+    define Kernel/SetInitramfs/PreConfigure
 	{ \
 		grep -v INITRAMFS $(2)/.config.old > $(2)/.config; \
 		echo 'CONFIG_INITRAMFS_SOURCE="$(call qstrip,$(CONFIG_EXTERNAL_CPIO))"' >> $(2)/.config; \
 	}
-      endef
-    endif
+    endef
   endif
 
   define Kernel/SetInitramfs
@@ -78,13 +68,11 @@ ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),y)
 		mv $(2)/.config $(2)/.config.old; \
 		$(call Kernel/SetInitramfs/PreConfigure,$(1),$(2)); \
 		echo "# CONFIG_INITRAMFS_PRESERVE_MTIME is not set" >> $(2)/.config; \
-		$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE),,echo "CONFIG_INITRAMFS_ROOT_UID=$(shell id -u)" >> $(2)/.config;) \
-		$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE),,echo "CONFIG_INITRAMFS_ROOT_GID=$(shell id -g)" >> $(2)/.config;) \
-		$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE), \
-			echo "# CONFIG_INITRAMFS_FORCE is not set" >> $(2)/.config;, \
-			$(if $(CONFIG_TARGET_INITRAMFS_FORCE), \
-				echo "CONFIG_INITRAMFS_FORCE=y" >> $(2)/.config;, \
-				echo "# CONFIG_INITRAMFS_FORCE is not set" >> $(2)/.config;)) \
+		echo "CONFIG_INITRAMFS_ROOT_UID=$(shell id -u)" >> $(2)/.config; \
+		echo "CONFIG_INITRAMFS_ROOT_GID=$(shell id -g)" >> $(2)/.config; \
+		$(if $(CONFIG_TARGET_INITRAMFS_FORCE), \
+			echo "CONFIG_INITRAMFS_FORCE=y" >> $(2)/.config;, \
+			echo "# CONFIG_INITRAMFS_FORCE is not set" >> $(2)/.config;) \
 		$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_NONE), \
 			echo "CONFIG_INITRAMFS_COMPRESSION_NONE=y" >> $(2)/.config;, \
 			echo "# CONFIG_INITRAMFS_COMPRESSION_NONE is not set" >> $(2)/.config; ) \
@@ -92,21 +80,33 @@ ifeq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),y)
 			$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_$(ALGO)), \
 				echo "CONFIG_INITRAMFS_COMPRESSION_$(ALGO)=y" >> $(2)/.config; $\, \
 				echo "# CONFIG_INITRAMFS_COMPRESSION_$(ALGO) is not set" >> $(2)/.config; $\) \
-			$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_$(ALGO)), \
-				echo "CONFIG_RD_$(ALGO)=y" >> $(2)/.config; $\, \
-				echo "# CONFIG_RD_$(ALGO) is not set" >> $(2)/.config; $\) \
 		) \
+		$(call Kernel/SetRamdiskCompression,$(2)/.config) \
 	}
   endef
 else
 endif
 
+define Kernel/SetRamdiskCompression
+	$(foreach ALGO,GZIP BZIP2 LZMA LZO XZ LZ4 ZSTD, \
+		$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_$(ALGO)), \
+			echo "CONFIG_RD_$(ALGO)=y" >> $(1); $\, \
+			echo "# CONFIG_RD_$(ALGO) is not set" >> $(1); $\) \
+	)
+endef
+
+# With a separate initramfs, the initramfs kernel differs from the regular
+# kernel only in ramdisk support. Enable it here too, so that one kernel
+# build serves both images.
 define Kernel/SetNoInitramfs
 	mv $(LINUX_DIR)/.config.set $(LINUX_DIR)/.config.old
 	grep -v INITRAMFS $(LINUX_DIR)/.config.old > $(LINUX_DIR)/.config.set
 	echo 'CONFIG_INITRAMFS_SOURCE=""' >> $(LINUX_DIR)/.config.set
 	echo '# CONFIG_INITRAMFS_FORCE is not set' >> $(LINUX_DIR)/.config.set
 	echo "# CONFIG_INITRAMFS_PRESERVE_MTIME is not set" >> $(LINUX_DIR)/.config.set
+	$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE), \
+		echo 'CONFIG_BLK_DEV_INITRD=y' >> $(LINUX_DIR)/.config.set; \
+		$(call Kernel/SetRamdiskCompression,$(LINUX_DIR)/.config.set))
 endef
 
 define Kernel/Configure/Default
@@ -180,15 +180,16 @@ endef
 ifneq ($(CONFIG_TARGET_ROOTFS_INITRAMFS),)
 # $1: Custom TARGET_DIR. If omitted TARGET_DIR is used.
 # $2: If defined Generate Per Rootfs Kernel Directory and use it
-# For Separate Initramf with $2 declared, skip kernel compile, it has
-# already been done previously on generic image build
+# For Separate Initramfs, the regular kernel is used as is, as its config
+# already has the ramdisk support (see Kernel/SetNoInitramfs)
 define Kernel/CompileImage/Initramfs
 	$(call locked,{ \
 		$(if $(2),$(call Kernel/PrepareConfigPerRootfs,$(LINUX_DIR)$(2));) \
-		$(call Kernel/Configure/Initramfs,$(if $(1),$(1),$(TARGET_DIR)),$(LINUX_DIR)$(2)); \
+		$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE),, \
+			$(call Kernel/Configure/Initramfs,$(if $(1),$(1),$(TARGET_DIR)),$(LINUX_DIR)$(2)); \
+			rm -rf $(LINUX_DIR)$(2)/usr/initramfs_data.cpio*;) \
 		$(CP) $(GENERIC_PLATFORM_DIR)/other-files/init $(if $(1),$(1),$(TARGET_DIR))/init; \
 		$(if $(SOURCE_DATE_EPOCH),touch -hcd "@$(SOURCE_DATE_EPOCH)" $(if $(1),$(1),$(TARGET_DIR)) $(if $(1),$(1),$(TARGET_DIR))/init;) \
-		rm -rf $(LINUX_DIR)$(2)/usr/initramfs_data.cpio*; \
 		$(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE), \
 			$(call locked,{ \
 				$(if $(call qstrip,$(CONFIG_EXTERNAL_CPIO)), \
@@ -210,8 +211,7 @@ define Kernel/CompileImage/Initramfs
 					$(STAGING_DIR_HOST)/bin/xz -T$(if $(filter 1,$(NPROC)),2,0) -9 -fz --check=crc32 $(KERNEL_BUILD_DIR)/initrd$(2).cpio;) \
 				$(if $(CONFIG_TARGET_INITRAMFS_COMPRESSION_ZSTD), \
 					$(STAGING_DIR_HOST)/bin/zstd -T0 -f -o $(KERNEL_BUILD_DIR)/initrd$(2).cpio.zstd $(KERNEL_BUILD_DIR)/initrd$(2).cpio;) \
-			}, gen-cpio$(2)); \
-			$(if $(2),,$(KERNEL_MAKE) $(KERNEL_MAKEOPTS_IMAGE) $(if $(KERNELNAME),$(KERNELNAME),all);),\
+			}, gen-cpio$(2));,\
 			$(KERNEL_MAKE) $(if $(2),-C $(LINUX_DIR)$(2)) $(KERNEL_MAKEOPTS_IMAGE) $(if $(KERNELNAME),$(KERNELNAME),all);) \
 		$(call Kernel/CopyImage,-initramfs,$(2)); \
 		$(if $(2),rm -rf $(LINUX_DIR)$(2);) \