diff --git a/package/gmp/gmp.mk b/package/gmp/gmp.mk
index bd401c6a80..7e8da9025c 100644
--- a/package/gmp/gmp.mk
+++ b/package/gmp/gmp.mk
@@ -14,6 +14,8 @@ GMP_CPE_ID_VENDOR = gmplib
 GMP_DEPENDENCIES = host-m4
 HOST_GMP_DEPENDENCIES = host-m4
 
+GMP_CONF_ENV += CC_FOR_BUILD="$(HOSTCC) -std=c99"
+
 # GMP doesn't support assembly for coldfire or mips r6 ISA yet
 # Disable for ARM v7m since it has different asm constraints
 ifeq ($(BR2_m68k_cf)$(BR2_MIPS_CPU_MIPS32R6)$(BR2_MIPS_CPU_MIPS64R6)$(BR2_ARM_CPU_ARMV7M),y)