diff --git a/configure.ac b/configure.ac
index 67fdfed..95d5571 100644
--- a/configure.ac
+++ b/configure.ac
@@ -36,10 +36,10 @@ AC_PROG_INSTALL
 AC_CHECK_HEADERS([endian.h sys/endian.h])
 AC_CHECK_DECLS([be32enc, be32dec, le32enc, le32dec,
     be64enc, be64dec, le64enc, le64dec], [], [], [[
-#ifdef HAVE_SYS_ENDIAN_H
+#if HAVE_SYS_ENDIAN_H
 #include <sys/endian.h>
 #endif
-#ifdef HAVE_ENDIAN_H
+#if HAVE_ENDIAN_H
 #include <endian.h>
 #endif
 ]])
@@ -48,7 +48,7 @@ AC_CHECK_FUNCS([strlcat strlcmp strlcpy])
 # For tracing allocations in unit tests
 AC_CHECK_HEADERS([sys/uio.h sys/ktrace.h], [], [], [[
 #include <sys/param.h>
-#ifdef HAVE_SYS_UIO_H
+#if HAVE_SYS_UIO_H
 #include <sys/uio.h>
 #endif
 ]])
diff --git a/include/cryb/endian.h b/include/cryb/endian.h
index 52ef8bb..d5ee47b 100644
--- a/include/cryb/endian.h
+++ b/include/cryb/endian.h
@@ -30,36 +30,36 @@
 #ifndef CRYB_ENDIAN_H_INCLUDED
 #define CRYB_ENDIAN_H_INCLUDED
 
-#ifdef HAVE_SYS_ENDIAN_H
+#if HAVE_SYS_ENDIAN_H
 #include <sys/endian.h>
 #endif
 
-#ifdef HAVE_ENDIAN_H
+#if HAVE_ENDIAN_H
 #include <endian.h>
 #endif
 
-#ifndef HAVE_DECL_BE32ENC
+#if !HAVE_DECL_BE32ENC
 #define be32enc cryb_be32enc
 #endif
-#ifndef HAVE_DECL_BE32DEC
+#if !HAVE_DECL_BE32DEC
 #define be32dec cryb_be32dec
 #endif
-#ifndef HAVE_DECL_BE64ENC
+#if !HAVE_DECL_BE64ENC
 #define be64enc cryb_be64enc
 #endif
-#ifndef HAVE_DECL_BE64DEC
+#if !HAVE_DECL_BE64DEC
 #define be64dec cryb_be64dec
 #endif
-#ifndef HAVE_DECL_LE32ENC
+#if !HAVE_DECL_LE32ENC
 #define le32enc cryb_le32enc
 #endif
-#ifndef HAVE_DECL_LE32DEC
+#if !HAVE_DECL_LE32DEC
 #define le32dec cryb_le32dec
 #endif
-#ifndef HAVE_DECL_LE64ENC
+#if !HAVE_DECL_LE64ENC
 #define le64enc cryb_le64enc
 #endif
-#ifndef HAVE_DECL_LE64DEC
+#if !HAVE_DECL_LE64DEC
 #define le64dec cryb_le64dec
 #endif
 
diff --git a/include/cryb/impl.h b/include/cryb/impl.h
index 614e659..ca3d925 100644
--- a/include/cryb/impl.h
+++ b/include/cryb/impl.h
@@ -30,7 +30,7 @@
 #ifndef CRYB_IMPL_H_INCLUDED
 #define CRYB_IMPL_H_INCLUDED
 
-#ifdef HAVE_CONFIG_H
+#if HAVE_CONFIG_H
 # include "config.h"
 #endif
 
diff --git a/include/cryb/strlcat.h b/include/cryb/strlcat.h
index 6f1fac2..64a3a7f 100644
--- a/include/cryb/strlcat.h
+++ b/include/cryb/strlcat.h
@@ -32,7 +32,7 @@
 
 size_t cryb_strlcat(char *, const char *, size_t);
 
-#ifndef HAVE_STRLCAT
+#if !HAVE_STRLCAT
 #undef strlcat
 #define strlcat(arg, ...) cryb_strlcat(arg, __VA_ARGS__)
 #endif
diff --git a/include/cryb/strlcmp.h b/include/cryb/strlcmp.h
index a8dff11..22b08b7 100644
--- a/include/cryb/strlcmp.h
+++ b/include/cryb/strlcmp.h
@@ -32,7 +32,7 @@
 
 int cryb_strlcmp(const char *, const char *, size_t);
 
-#ifndef HAVE_STRLCMP
+#if !HAVE_STRLCMP
 #undef strlcmp
 #define strlcmp(...) cryb_strlcmp(__VA_ARGS__)
 #endif
diff --git a/include/cryb/strlcpy.h b/include/cryb/strlcpy.h
index 8c17081..ee80bd2 100644
--- a/include/cryb/strlcpy.h
+++ b/include/cryb/strlcpy.h
@@ -32,7 +32,7 @@
 
 size_t cryb_strlcpy(char *, const char *, size_t);
 
-#ifndef HAVE_STRLCPY
+#if !HAVE_STRLCPY
 #undef strlcpy
 #define strlcpy(arg, ...) cryb_strlcpy(arg, __VA_ARGS__)
 #endif
diff --git a/lib/digest/sha1.c b/lib/digest/sha1.c
index a65d960..e5277de 100644
--- a/lib/digest/sha1.c
+++ b/lib/digest/sha1.c
@@ -30,11 +30,11 @@
 
 #include "cryb/impl.h"
 
-#ifdef HAVE_SYS_ENDIAN_H
+#if HAVE_SYS_ENDIAN_H
 #include <sys/endian.h>
 #endif
 
-#ifdef HAVE_ENDIAN_H
+#if HAVE_ENDIAN_H
 #define _BSD_SOURCE
 #include <endian.h>
 #endif
diff --git a/lib/mac/hmac_sha1.c b/lib/mac/hmac_sha1.c
index 9db040d..c768154 100644
--- a/lib/mac/hmac_sha1.c
+++ b/lib/mac/hmac_sha1.c
@@ -30,11 +30,11 @@
 
 #include "cryb/impl.h"
 
-#ifdef HAVE_SYS_ENDIAN_H
+#if HAVE_SYS_ENDIAN_H
 #include <sys/endian.h>
 #endif
 
-#ifdef HAVE_ENDIAN_H
+#if HAVE_ENDIAN_H
 #define _BSD_SOURCE
 #include <endian.h>
 #endif
diff --git a/lib/mac/hmac_sha224.c b/lib/mac/hmac_sha224.c
index 936bd17..0c043c7 100644
--- a/lib/mac/hmac_sha224.c
+++ b/lib/mac/hmac_sha224.c
@@ -30,11 +30,11 @@
 
 #include "cryb/impl.h"
 
-#ifdef HAVE_SYS_ENDIAN_H
+#if HAVE_SYS_ENDIAN_H
 #include <sys/endian.h>
 #endif
 
-#ifdef HAVE_ENDIAN_H
+#if HAVE_ENDIAN_H
 #define _BSD_SOURCE
 #include <endian.h>
 #endif
diff --git a/lib/mac/hmac_sha256.c b/lib/mac/hmac_sha256.c
index 1b45c49..2947676 100644
--- a/lib/mac/hmac_sha256.c
+++ b/lib/mac/hmac_sha256.c
@@ -30,11 +30,11 @@
 
 #include "cryb/impl.h"
 
-#ifdef HAVE_SYS_ENDIAN_H
+#if HAVE_SYS_ENDIAN_H
 #include <sys/endian.h>
 #endif
 
-#ifdef HAVE_ENDIAN_H
+#if HAVE_ENDIAN_H
 #define _BSD_SOURCE
 #include <endian.h>
 #endif
diff --git a/lib/mac/hmac_sha384.c b/lib/mac/hmac_sha384.c
index 8864c6f..22a94c3 100644
--- a/lib/mac/hmac_sha384.c
+++ b/lib/mac/hmac_sha384.c
@@ -30,11 +30,11 @@
 
 #include "cryb/impl.h"
 
-#ifdef HAVE_SYS_ENDIAN_H
+#if HAVE_SYS_ENDIAN_H
 #include <sys/endian.h>
 #endif
 
-#ifdef HAVE_ENDIAN_H
+#if HAVE_ENDIAN_H
 #define _BSD_SOURCE
 #include <endian.h>
 #endif
diff --git a/lib/mac/hmac_sha512.c b/lib/mac/hmac_sha512.c
index 3d7f0a4..7308fde 100644
--- a/lib/mac/hmac_sha512.c
+++ b/lib/mac/hmac_sha512.c
@@ -30,11 +30,11 @@
 
 #include "cryb/impl.h"
 
-#ifdef HAVE_SYS_ENDIAN_H
+#if HAVE_SYS_ENDIAN_H
 #include <sys/endian.h>
 #endif
 
-#ifdef HAVE_ENDIAN_H
+#if HAVE_ENDIAN_H
 #define _BSD_SOURCE
 #include <endian.h>
 #endif
diff --git a/t/t_malloc.c b/t/t_malloc.c
index 4a0f952..f1851f6 100644
--- a/t/t_malloc.c
+++ b/t/t_malloc.c
@@ -40,9 +40,9 @@
 #define MAP_NOSYNC 0
 #endif
 
-#ifdef HAVE_UTRACE
-#ifdef HAVE_SYS_KTRACE_H
-#ifdef HAVE_SYS_UIO_H
+#if HAVE_UTRACE
+#if HAVE_SYS_KTRACE_H
+#if HAVE_SYS_UIO_H
 #include <sys/uio.h>
 #endif
 #include <sys/ktrace.h>