diff --git a/Makefile b/Makefile
index e649606..5bd2643 100644
--- a/Makefile
+++ b/Makefile
@@ -46,13 +46,13 @@ TARGET = bin/selfhost/lacc
 
 bin/lacc: $(SOURCES)
 	@mkdir -p $(@D)
-	$(CC) -std=c89 -g $(CFLAGS) -Iinclude src/lacc.c -o $@ \
+	$(CC) -std=c99 -g $(CFLAGS) -Iinclude src/lacc.c -o $@ \
 		-D'LACC_STDLIB_PATH="$(LIBDIR_SOURCE)"' \
 		-DAMALGAMATION
 
 bin/release/lacc: $(SOURCES)
 	@mkdir -p $(@D)
-	$(CC) -std=c89 -O3 $(CFLAGS) -Iinclude src/lacc.c -o $@ \
+	$(CC) -std=c99 -O3 $(CFLAGS) -Iinclude src/lacc.c -o $@ \
 		-D'LACC_STDLIB_PATH="$(LIBDIR_TARGET)"' \
 		-DAMALGAMATION \
 		-DNDEBUG
@@ -61,7 +61,7 @@ bin/bootstrap/lacc: bin/lacc
 	@mkdir -p $(@D)
 	for file in $(SOURCES) ; do \
 		target=$(@D)/$$(basename $$file .c).o ; \
-		$? -std=c89 -fPIC -Iinclude -c $$file -o $$target \
+		$? -std=c99 -fPIC -Iinclude -c $$file -o $$target \
 			-D'LACC_STDLIB_PATH="$(LIBDIR_SOURCE)"' ; \
 	done
 	$(CC) $(@D)/*.o -o $@
@@ -71,7 +71,7 @@ bin/selfhost/lacc: bin/bootstrap/lacc
 	for file in $(SOURCES) ; do \
 		name=$$(basename $$file .c) ; \
 		target=$(@D)/$${name}.o ; \
-		$? -std=c89 -fPIC -Iinclude -c $$file -o $$target \
+		$? -std=c99 -fPIC -Iinclude -c $$file -o $$target \
 			-D'LACC_STDLIB_PATH="$(LIBDIR_SOURCE)"' ; \
 		diff bin/bootstrap/$${name}.o $$target ; \
 	done
diff --git a/src/backend/x86_64/dwarf.c b/src/backend/x86_64/dwarf.c
index 4de1710..3cae886 100644
--- a/src/backend/x86_64/dwarf.c
+++ b/src/backend/x86_64/dwarf.c
@@ -8,6 +8,7 @@
 #include <lacc/context.h>
 
 #include <assert.h>
+#include <stdarg.h>
 
 /* Unit header. Only generate compile units. */
 #define DW_UT_compile 0x01