diff --git a/configure.ac b/configure.ac
index ec5003f6..762ca9f9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -189,7 +189,9 @@ AC_CHECK_FUNCS([clock_gettime], [CLOCK_LIB=],
                              [AC_MSG_ERROR([Couldn't find clock_gettime])])])
 AC_SUBST([CLOCK_LIB])
 
-AC_CHECK_FUNCS([open_memstream], [HAVE_OPEN_MEMSTREAM=yes])
+AC_CHECK_FUNCS([open_memstream],
+               [AC_DEFINE([HAVE_OPEN_MEMSTREAM], 1, [Have open_memstream()])],
+               [AC_DEFINE([HAVE_OPEN_MEMSTREAM], 0)])
 
 dnl Use lots of warning flags with with gcc and compatible compilers
 
diff --git a/intel/test_decode.c b/intel/test_decode.c
index b4eddcd1..68f777b0 100644
--- a/intel/test_decode.c
+++ b/intel/test_decode.c
@@ -91,7 +91,7 @@ compare_batch(struct drm_intel_decode *ctx, const char *batch_filename)
 {
 	FILE *out = NULL;
 	void *ptr, *ref_ptr, *batch_ptr;
-#ifdef HAVE_OPEN_MEMSTREAM
+#if HAVE_OPEN_MEMSTREAM
 	size_t size;
 #endif
 	size_t ref_size, batch_size;
@@ -109,7 +109,7 @@ compare_batch(struct drm_intel_decode *ctx, const char *batch_filename)
 	 * figure out how to output to a file in a safe and sane way
 	 * inside of an automake project's test infrastructure.
 	 */
-#ifdef HAVE_OPEN_MEMSTREAM
+#if HAVE_OPEN_MEMSTREAM
 	out = open_memstream((char **)&ptr, &size);
 #else
 	fprintf(stderr, "platform lacks open_memstream, skipping.\n");
diff --git a/meson.build b/meson.build
index 2a6c4680..50daa1d0 100644
--- a/meson.build
+++ b/meson.build
@@ -196,9 +196,7 @@ if cc.has_header_symbol('sys/sysmacros.h', 'major')
 elif cc.has_header_symbol('sys/mkdev.h', 'major')
   config.set10('MAJOR_IN_MKDEV', true)
 endif
-if cc.has_function('open_memstream')
-  config.set10('HAVE_OPEN_MEMSTREAM', true)
-endif
+config.set10('HAVE_OPEN_MEMSTREAM', cc.has_function('open_memstream'))
 
 warn_c_args = []
 foreach a : ['-Wall', '-Wextra', '-Wsign-compare', '-Werror=undef',