diff --git a/package/libkrb5/libkrb5.mk b/package/libkrb5/libkrb5.mk
index e57a2b98a2..d0ec877d35 100644
--- a/package/libkrb5/libkrb5.mk
+++ b/package/libkrb5/libkrb5.mk
@@ -16,6 +16,8 @@ LIBKRB5_CPE_ID_PRODUCT = kerberos_5
 LIBKRB5_DEPENDENCIES = host-bison $(TARGET_NLS_DEPENDENCIES)
 LIBKRB5_INSTALL_STAGING = YES
 
+LIBKRB5_CFLAGS = $(TARGET_CFLAGS) -std=gnu99
+
 # The configure script uses AC_TRY_RUN tests to check for those values,
 # which doesn't work in a cross-compilation scenario. Therefore,
 # we feed the configure script with the correct answer for those tests
@@ -38,9 +40,11 @@ LIBKRB5_CONF_OPTS = \
 # Error: selected processor does not support `mcr p15,0,r2,c7,c10,5' in Thumb mode
 # so, we deactivate Thumb mode
 ifeq ($(BR2_ARM_INSTRUCTIONS_THUMB),y)
-LIBKRB5_CONF_ENV += CFLAGS="$(TARGET_CFLAGS) -marm"
+LIBKRB5_CFLAGS += -marm
 endif
 
+LIBKRB5_CONF_ENV += CFLAGS="$(LIBKRB5_CFLAGS)"
+
 # Enabling static and shared at the same time is not supported
 ifeq ($(BR2_SHARED_STATIC_LIBS),y)
 LIBKRB5_CONF_OPTS += --disable-static