diff --git a/common/scaler/scalebit.cpp b/common/scaler/scalebit.cpp
index 9c697df7742..4bb5e0a8166 100644
--- a/common/scaler/scalebit.cpp
+++ b/common/scaler/scalebit.cpp
@@ -33,14 +33,14 @@
  * - derivative works of the program are allowed.
  */
 
-#if HAVE_CONFIG_H
+#if defined(HAVE_CONFIG_H)
 #include <config.h>
 #endif
 
 #include "scale2x.h"
 #include "scale3x.h"
 
-#if HAVE_ALLOCA_H
+#if defined(HAVE_ALLOCA_H)
 #include <alloca.h>
 #endif
 
@@ -256,7 +256,7 @@ static void scale4x(void* void_dst, unsigned dst_slice, const void* void_src, un
 
 	mid_slice = (mid_slice + 0x7) & ~0x7; /* align to 8 bytes */
 
-#if HAVE_ALLOCA
+#if defined(HAVE_ALLOCA)
 	mid = alloca(6 * mid_slice); /* allocate space for 6 row buffers */
 
 	assert(mid != 0); /* alloca should never fails */
@@ -269,7 +269,7 @@ static void scale4x(void* void_dst, unsigned dst_slice, const void* void_src, un
 
 	scale4x_buf(void_dst, dst_slice, mid, mid_slice, void_src, src_slice, pixel, width, height);
 
-#if !HAVE_ALLOCA
+#if !defined(HAVE_ALLOCA)
 	free(mid);
 #endif
 }