diff --git a/drivers/base/firmware_loader/builtin/Makefile b/drivers/base/firmware_loader/builtin/Makefile
index 37e5ae387400..4a66888e7253 100644
--- a/drivers/base/firmware_loader/builtin/Makefile
+++ b/drivers/base/firmware_loader/builtin/Makefile
@@ -8,7 +8,8 @@ fwdir := $(addprefix $(srctree)/,$(filter-out /%,$(fwdir)))$(filter /%,$(fwdir))
 obj-y  := $(addsuffix .gen.o, $(subst $(quote),,$(CONFIG_EXTRA_FIRMWARE)))
 
 FWNAME    = $(patsubst $(obj)/%.gen.S,%,$@)
-FWSTR     = $(subst /,_,$(subst .,_,$(subst -,_,$(FWNAME))))
+comma     := ,
+FWSTR     = $(subst $(comma),_,$(subst /,_,$(subst .,_,$(subst -,_,$(FWNAME)))))
 ASM_WORD  = $(if $(CONFIG_64BIT),.quad,.long)
 ASM_ALIGN = $(if $(CONFIG_64BIT),3,2)
 PROGBITS  = $(if $(CONFIG_ARM),%,@)progbits