--- a/Makefile
+++ b/Makefile
@@ -33,7 +33,7 @@ SOURCES := $(shell find src -name '*.cr')
 SPEC_SOURCES := $(shell find spec -name '*.cr')
 override FLAGS += -D strict_multi_assign -D preview_overload_order $(if $(release),--release )$(if $(stats),--stats )$(if $(progress),--progress )$(if $(threads),--threads $(threads) )$(if $(debug),-d )$(if $(static),--static )$(if $(LDFLAGS),--link-flags="$(LDFLAGS)" )$(if $(target),--cross-compile --target $(target) )$(if $(interpreter),,-Dwithout_interpreter )
 SPEC_WARNINGS_OFF := --exclude-warnings spec/std --exclude-warnings spec/compiler --exclude-warnings spec/primitives
-SPEC_FLAGS := $(if $(verbose),-v )$(if $(junit_output),--junit_output $(junit_output) )$(if $(order),--order=$(order) )
+SPEC_FLAGS := $(if $(verbose),-v )$(if $(junit_output),--junit_output $(junit_output) )$(if $(order),--order=$(order) )$(EXTRA_SPEC_FLAGS)
 CRYSTAL_CONFIG_LIBRARY_PATH := '$$ORIGIN/../lib/crystal'
 CRYSTAL_CONFIG_BUILD_COMMIT := $(shell git rev-parse --short HEAD 2> /dev/null)
 CRYSTAL_CONFIG_PATH := '$$ORIGIN/../share/crystal/src'