diff --git a/configure.ac b/configure.ac
index e5ae62fc62..332fb83b58 100644
--- a/configure.ac
+++ b/configure.ac
@@ -183,8 +183,8 @@ AC_ARG_ENABLE([pb-tests],
     # AC_CHECK_PROG(PROTOC_GEN_YARA, protoc-gen-yara, protoc-gen-yara)
     # AS_IF([test "x${PROTOC_GEN_YARA}" == "x"],
     #    [AC_MSG_ERROR([please install https://github.com/VirusTotal/protoc-gen-yara])])
-    PKG_CHECK_MODULES(PROTOBUF_C, libprotobuf-c >= 1.0.0)
-    AC_CHECK_LIB(protobuf-c, protobuf_c_message_unpack,,
+    PKG_CHECK_MODULES([PROTOBUF_C], [libprotobuf-c >= 1.0.0])
+    AC_CHECK_LIB([protobuf-c], protobuf_c_message_unpack,,
       AC_MSG_ERROR([please install libprotobuf-c library]))
     CFLAGS="$CFLAGS -DPB_TESTS_MODULE"
     PC_REQUIRES_PRIVATE="$PC_REQUIRES_PRIVATE libprotobuf-c"