diff --git a/Configurations/unix-Makefile.tmpl b/Configurations/unix-Makefile.tmpl
index f3e3a98981..b6f9a52f9d 100644
--- a/Configurations/unix-Makefile.tmpl
+++ b/Configurations/unix-Makefile.tmpl
@@ -1205,10 +1205,18 @@ lint: ## Evaluate C code via "splint"
            echo splint -DLINT -posixlib -preproc -D__gnuc_va_list=void \
 	   -I. -Iinclude -Iapps/include $(CRYPTOHEADERS) $(SSLHEADERS) $(SRCS) )
 
-.PHONY: check-format
-check-format: ## Evaluate C code according to OpenSSL coding standards
-	( cd $(SRCDIR); $(PERL) util/check-format.pl \
-			$(SRCS) \$(CRYPTOHEADERS) $(SSLHEADERS) )
+CLANG_FORMAT_DIFF = clang-format-diff
+
+.PHONY: check-format check-clang-format-diff-cmd
+check-clang-format-diff-cmd:
+	@if ! command -v "$(CLANG_FORMAT_DIFF)" >/dev/null; then \
+		echo "Unable to find ${CLANG_FORMAT_DIFF}";\
+		echo "Please set the CLANG_FORMAT_DIFF variable to your clang-format-diff command";\
+		exit 1;\
+	fi
+
+check-format: check-clang-format-diff-cmd ## Evaluate C code according to OpenSSL coding standards
+	( cd $(SRCDIR); git diff -U0 --no-prefix --no-color | $(CLANG_FORMAT_DIFF) )
 
 generate_apps:
 	( cd $(SRCDIR); $(PERL) VMS/VMSify-conf.pl \