diff --git a/src/os/unix/crashlog_unix.cpp b/src/os/unix/crashlog_unix.cpp
index ee86cb5eeb..5f17fafdb9 100644
--- a/src/os/unix/crashlog_unix.cpp
+++ b/src/os/unix/crashlog_unix.cpp
@@ -27,6 +27,10 @@
 #	include <dlfcn.h>
 #endif
 
+#if defined(__NetBSD__)
+#include <unistd.h>
+#endif
+
 /**
  * Unix implementation for the crash logger.
  */
diff --git a/src/stdafx.h b/src/stdafx.h
index b961622663..8a8595722b 100644
--- a/src/stdafx.h
+++ b/src/stdafx.h
@@ -24,9 +24,6 @@
 #elif defined(__NDS__)
 	#include <nds/jtypes.h>
 	#define TROUBLED_INTS
-#elif defined(__NetBSD__)
-	#include <unistd.h>
-	#define _GNU_SOURCE
 #endif
 
 /* It seems that we need to include stdint.h before anything else
diff --git a/src/string_func.h b/src/string_func.h
index 2ff5f04399..942873593a 100644
--- a/src/string_func.h
+++ b/src/string_func.h
@@ -246,13 +246,18 @@ static inline bool IsWhitespace(WChar c)
 	;
 }
 
-#ifndef _GNU_SOURCE
+/* Needed for NetBSD version (so feature) testing */
+#ifdef __NetBSD__
+#include <sys/param.h>
+#endif
+
+#if !defined(_GNU_SOURCE) && !(defined(__NetBSD_Version__) && 400000000 < __NetBSD_Version__ )
 /* strndup is a GNU extension */
 char *strndup(const char *s, size_t len);
 #endif /* !_GNU_SOURCE */
 
 /* strcasestr is available for _GNU_SOURCE, BSD and some Apple */
-#if defined(_GNU_SOURCE) || (defined(__BSD_VISIBLE) && __BSD_VISIBLE) || (defined(__APPLE__) && (!defined(_POSIX_C_SOURCE) || defined(_DARWIN_C_SOURCE)))
+#if defined(_GNU_SOURCE) || (defined(__BSD_VISIBLE) && __BSD_VISIBLE) || (defined(__APPLE__) && (!defined(_POSIX_C_SOURCE) || defined(_DARWIN_C_SOURCE))) || _NETBSD_SOURCE
 #	undef DEFINE_STRCASESTR
 #else
 #	define DEFINE_STRCASESTR