diff --git a/makefile b/makefile
index 59983c2..db87334 100644
--- a/makefile
+++ b/makefile
@@ -84,7 +84,7 @@ LDFLAGS += -ldl
 endif
 endif
 
-CFLAGS+=-w -Wall -DNDEBUG -DUSE_THREADS  -fstrict-aliasing -Iext -Iext/lz4/lib -Iext/simdcomp/include -Iext/MaskedVByte/include -Iext/LittleIntPacker/include -Iext/streamvbyte/include $(DEFS)
+CFLAGS+=-w -Wall -std=gnu99 -DNDEBUG -DUSE_THREADS  -fstrict-aliasing -Iext -Iext/lz4/lib -Iext/simdcomp/include -Iext/MaskedVByte/include -Iext/LittleIntPacker/include -Iext/streamvbyte/include $(DEFS)
 CXXFLAGS+=$(DDEBUG) $(MARCH) -std=gnu++11 -w -fpermissive -Wall -fno-rtti $(DEFS) -Iext/FastPFor/headers
 
 all: icbench idxcr idxqry idxseg